Definition of standard office environments for evaluating the impact of office furniture emissions on indoor VOC concentrations
Randal D Carter
An evolving variety of sometimes conflicting test methods, model office environments, and requirements for modeling volatile organic compound (VOC) emissions from office furniture have been specified by various US organizations from 1989 to the present (Washington 1989; US EPA 1996; US EPA 1999; California 2000; Greenguard 2001; California 2004; USGBC 2004; BIFMA 2005a, 2005b; SCS 2005; California 2006). In these varied programs, environmental chamber testing of office furniture workstations or components is used to determine the emission rates, which are in turn used to estimate the impact of the workstation system on the VOC concentration levels in actual buildings by using a prescribed office environment model (i.e., occupant exposure scenario). Some of these programs define office environment models that are intended to be representative of specific buildings (Washington 1989; US EPA 1996; California 2000), while others do not contain any office environment model (US EPA 1999). The proliferation of office furniture emission programs with varied and potentially outdated office environment models raises questions as to how well the models represent actual building environments and makes it extremely difficult to compare VOC emissions performance across the broad variety of office furniture types available today.
The objective of this study is to define a standard, representative “worst-case” office environment model for new office furniture used in North American office buildings. This office environment model is intended to be used to provide a common basis of comparison for a broad variety of office furniture to relevant emissions requirements. These comparisons to requirements generally occur when estimating the impact of office furniture emissions on indoor VOC concentrations using the results of environmental chamber emissions testing. This study was conducted jointly with a working group of the Business and Institutional Furniture Manufacturers Association (BIFMA) (1) International, Furniture Emissions Standard (FES) Subcommittee, in support of the development of the BIFMA M7.1-2005 standard test method.
In 1994 the United States General Services Administration (GSA) requested that BIFMA develop a harmonized, voluntary, open consensus standard for office furniture emissions testing. Work began and in 1998 BIFMA filed public notice through the ANSI Project Initiation Notification System (PINS) announcing the ongoing development of a draft ANSI standard for office furniture emissions. In parallel with this work, BIFMA, along with the US Environmental Protection Agency (EPA), the Research Triangle Institute, and other relevant stakeholders, helped to develop the US EPA 1999 test protocol for large chamber emissions testing of office furniture. BIFMA FES work continued, reaffirming the ANSI PINS for office furniture emission standards in 2004 and leading to a test method development project, including this study, which was conducted in 2005. The results of this study have been incorporated into the BIFMA M7.1-2005 test method, which was issued by BIFMA following industry consensus in September 2005 and adopted as an alternative compliance path within the United States Green Building Council (USGBC) Leadership in Energy and Environmental Design for Commercial Interiors (LEED-CI) Environmental Quality (EQ) credit 4.5 for low-emitting furnishings on July 12, 2006. The state governments of California and Minnesota have incorporated the BIFMA M7.1 test method into their respective procurement specifications for office furniture. Scientific Certification Systems (www.scscertified.com) has also adopted the BIFMA M7.1 test method as part of their Indoor Advantage[TM] certification program. (2)
An office environment model defines the size and volume of the office space, the amount and type of office furniture surface area, and the outdoor, clean airflow rate. In this study, 31 randomly selected floor plans from North American office buildings were analyzed in detail. The floor plans were from current projects (late 2004 and early 2005) and were provided by an industry cross section of seven major office furniture manufacturers (see “Acknowledgments”). The analysis included documenting the potential emitting surface area for each workstation and determining how much common office space (aisles, etc.) was present as shared between workstations and other adjoining spaces. The 90th percentile conditions for total furniture surface area within the 50th percentile workstation footprint sizes were identified from the more than 5000 workstations analyzed, to provide a representative “worst-case” office environment model for estimating the impact of office furniture emissions on VOC concentrations.
This study is based on analysis of office floor plan drawings and related furniture dimensions. These drawings did not include measurements or specifications of ceiling heights or the airflow levels present in each building. Therefore, the requirements of ANSI/ASHRAE Standard 62-2001 and ANSI/ASHRAE Standard 62.1-2004 were used to determine the minimum amount of outdoor, clean airflow required in order to determine a representative “worst-case” office environment model. The two ASHRAE 62.1 standards were used because most US jurisdictions specify ASHRAE 62 as a minimum legal ventilation requirement within building codes and the USGBC has specified ANSI/ASHRAE Standard 62.1- 2004 as a prerequisite requirement for LEED projects. For determinations of office volume, a 2.74 m (9 ft) ceiling height has been assumed as a representative “worst-case” condition. The authors note the Standard 62.1 criteria and the emissions concentration calculations are based on steady-state environments, which are dependent on airflow rates (cfm or L/s) and not room volumes.
THE OFFICE ENVIRONMENT MODEL–THE MISSING FACTORS
The office environment model is used to estimate the impact of office furniture emissions on indoor VOC concentrations using the following equation (reference BIFMA M7.1-2005, Section 6.6).
Equation 1 calculates the VOC concentration in the office environment due to the measured emissions from an office workstation system.
C(t) = [[[A.sub.0]E(t)]/[Q.sub.0]] (1)
C(t) = VOC concentration in the defined office environment at the time (t) of interest, mg/[m.sup.3]
[A.sub.o] = source amount of office furniture workstation, i.e., emitting surface area present, [m.sup.2]
E(t) = measured emission factor of office workstation at time (t) of interest, mg/([m.sup.2] h)
[Q.sub.o] = the outdoor, clean air ventilation flow rate in the office environment, [m.sup.3]/h
The VOC concentration C(t) due to office furniture can be calculated, and the emission factor E(t) can be measured from chamber testing, but the challenge is to determine the appropriate amount of emitting surface area [A.sub.0] and the outdoor, clean air ventilation flow rate [Q.sub.0] to use in the office environment exposure model. From Equation 1 it is evident that more emitting surface area [A.sub.0] will result in a higher VOC concentration, while more outdoor, clean airflow [Q.sub.0] will result in a lower VOC concentration. Therefore, it is necessary to determine the representative “worst-case” conditions for both [A.sub.0] and [Q.sub.0] in combination, i.e., under what reasonable conditions will there be the most office furniture surface area with the least amount of outdoor, clean airflow?
Determination of Outdoor, Clean Airflow Rate [Q.sub.0]
US building codes define the minimum legal requirements for building design and construction. While each jurisdiction or municipality is responsible for determining their specific requirements, the vast majority adopt existing model codes or standards. Specifically for building ventilation, most jurisdictions establish minimum criteria based on ASHRAE standards. The most widely adopted model code for building mechanical heating, ventilating, and cooling systems, the International Code Council’s International Mechanical Code (IMC 2003) specifies in Section 403 that building ventilation systems must provide a minimum outdoor, clean airflow rate to occupied spaces based on room occupancy type (3) (e.g., office, conference room, corridor, kitchen, etc.) and occupant density (i.e., persons present per unit of net occupiable floor area) as defined in ASHRAE Standard 62-2001. Future revisions of building codes are expected to adopt the ASHRAE 62.1-2004 standard. As previously mentioned, the USGBC LEED program (USGBC 2004) has also adopted the ASHRAE 62.1-2004 standard as a prerequisite requirement for receiving the 15 possible points under “Indoor Environmental Quality.”
ASHRAE 62-2001 requires a minimum of 10 L/s per person (20 cfm per person) of outdoor, clean air ventilation for office spaces. ASHRAE 62-2001 also specifies an estimated maximum occupant density for office spaces of seven people per 100 [m.sup.2] or 1000 f[t.sup.2] of net occupiable space. However, the Ventilation Rate Procedure in ASHRAE 62.1-2004, Section 6, determines the minimum outdoor, clean air ventilation rate using Equation 2, the ASHRAE 62.1-2004 calculation of minimum required outdoor airflow:
[V.sub.bz] = [R.sub.p][P.sub.z] + [R.sub.a][A.sub.z] (2)
[V.sub.bz] = outdoor, clean airflow rate required in the breathing zone of the occupiable space(s)
[R.sub.p] = outdoor, clean airflow rate required per person, 2.5 L/s per person (5 cfm per person) for office spaces
[P.sub.z] = population, the number of persons expected to occupy the zone during typical usage
[R.sub.a] = outdoor, clean airflow rate required per unit area, 0.3 (L/s)/[m.sup.2] (0.06 cfm/[ft.sup.2]) for office spaces
[A.sub.z] = zone floor area: the net occupiable floor area of the zone, [m.sup.2] (f[t.sup.2])
ASHRAE 62.1-2004 also specifies a default occupant density for office spaces of five people per 100 [m.sup.2] or 1000 [ft.sup.2] of net occupiable space when actual occupant density is not known.
Comparing ASHRAE 62-2001 and ASHRAE 62.1-2004, the minimum required outdoor, clean airflow ventilation rates are determined differently. While ASHRAE 62-2001 requires 20 cfm of outdoor, clean air per person regardless of occupant density, ASHRAE 62.1-2004 varies the requirement for outdoor, clean air in an office space by both the number of occupants present and the office floor area per person in the space, as shown in Figure 1.
Assuming that each office workstation is intended for a single person (an assumption that is conservative for larger workstations with more space that may be used for meetings), office spaces with lower occupant density (depicted on the right side of Figure 1) have correspondingly larger workstations and therefore have the potential for correspondingly larger furniture emitting surface areas. Similarly, office spaces with higher occupant densities (depicted on the left side of Figure 1) have correspondingly smaller workstations and due to limited space will have correspondingly smaller furniture emitting surface areas.
Under ASHRAE 62-2001 with a constant 20 cfm per person of outdoor, clean air requirement, regardless of occupant density or workstation size, the representative “worstcase” condition would tend to be larger workstations with low occupant density and the potential for more furniture surface area. However, under ASHRAE 62.1-2004, which requires more outdoor, clean air ventilation for larger workstations, with potentially more furniture surface area and less outdoor, clean air ventilation for smaller workstations with correspondingly less furniture surface area, neither larger nor smaller workstations provide an obvious representative “worst case” condition for potential furniture emission concentration. Considering new office workstation sizes (described in the next section), ASHRAE 62.1-2004 is a more stringent requirement and was chosen to determine the outdoor, clean airflow rate [Q.sub.0], as the vast majority of new office workstations are smaller than 250 [ft.sup.2], which would result in a ventilation rate less than 20 cfm/person (Figure 1).
Investigation of Office Workstation Size
Conceptually, the office environment model can be considered to be a room, ventilated with some outdoor, clean airflow rate, and containing a single office workstation with an amount of common office space distributed around the workstation for aisles, shared copiers, storage, etc. As with airflow, the amount and type of office furniture surface area present is dependent on the size of the office space. Therefore, it is necessary to determine the floor area per workstation and floor area of associated common office space.
Various sources of research exist regarding the size of office workstations in existing buildings (IFMA 1997, 2002; Veitch 2003; Persily and Gorfain 2004); however, the authors could not identify existing research that specifically addressed office workstation sizes for buildings with new furniture (representing new office workstation applications and trends). Existing research and office furniture manufacturer experience firmly supports the trend that installed office workstation footprints have been shrinking. “Eight years of research by the International Facility Management Association (IFMA) shows that, across the board in all categories, workers in US offices have been forced to adapt to progressively less space. Surveys of facility professionals in 1994, 1997 and 2002 show that the average amount of square footage allotted to each worker has decreased continuously” (IFMA 2004).
Given the open plan nature of many office buildings, workstations and the surrounding “common” space are affected by the contents, dimensions, and configuration of the entire office floor plan. US building code and ASHRAE ventilation criteria are also directly affected by the entire floor plan. Therefore, the analysis of workstation size necessarily began with office building floor plans. A working group of volunteers from the BIFMA Furniture Emissions Standard subcommittee, representing seven major office furniture manufacturers, agreed to provide and help analyze a random sample of customer floor plans from late 2004 to early 2005 projects. At the time plans were selected, the analysis plan had not been fully defined or completed and participants did not know what effect large or small buildings, large or small workstations, or other variable parameters could have on the analysis. Participants were asked to randomly select floor plans from current projects but to focus on plans that contained as much dimensional detail as possible of all included office furniture.
To maintain consistency within the analysis of floor plan area and to apportion any common office space to adjoining areas likely to share ventilation, the following steps were conducted for each floor plan.
First, determine the total usable floor area. Considering the ASHRAE 62.1-2004 definition for net occupiable space and reviewing definitions for usable floor area from existing office building floor area measurement standards (ANSI/ BOMA 1996; ASTM E1836-01), for purposes of this study total usable floor area is defined as gross interior building area minus major vertical penetrations minus building common area. Vertical penetrations typically include stairwells, elevators, plenum shafts, etc. Building common area provides services to building tenants but is not located within the office area of any specific tenant and typically includes utility/ mechanical rooms, restrooms, janitor closets, lobbies, etc. Also exclude occupiable non-office areas, such as cafeterias and kitchens, unless they were immediately adjoining (i.e., are open to or have doors that open directly into) the general office common space (see Figure 2). General office common space usually functions as a walkway or aisle, and may be used as an open conference/gathering area, fax/copier work area, or a combination of similar functions. If occupiable non-office areas are immediately adjoining, then treat these spaces as another “area of interest” when apportioning general office common space unless the doors separating these spaces from the general office common space would normally be closed the vast majority of the time (e.g., public reception areas or corridors outside elevators in multiple-story buildings with multiple tenants).
Second, determine the total conference room floor area of all conference rooms shown on the plan and the total corridor floor area of all floor-to-ceiling corridors shown on the plan. Exclude conferencing areas that are part of a private office or an open plan area. Corridors must be enclosed on at least three sides with floor-to-ceiling walls or doors.
Third, calculate the open plan usable floor area and private office usable floor area. The open plan usable floor area is the total floor space occupied by all open plan workstations, plus a proportionally allocated portion of the general office common space. To calculate the open plan usable floor area, the total space occupied by all open plan workstations is divided by the total floor space of all “areas of interest” and then multiplied by the total usable floor area (see Figure 2). “Areas of Interest” are occupiable building areas (e.g., private offices, floor-to-ceiling conference rooms, pure corridor space, etc.) that immediately adjoin the general office space, usually surrounding open plan offices or immediately adjacent to private offices. Private office usable area is calculated similarly but uses total floor space occupied by all private offices instead of open plan workstations. To allow apportioning of general office common space to individual open plan and private office workstations, the ratio specific to each floor plan of common area apportioned to the open plan and private offices is calculated as shown in Equation 3. The resulting floor area data for each building floor plan are shown in Tables 1 and 2.
Table 1. Floor Area–Measured Values from Building Floor Plans
Floor Plan Total Total All Total All Total Other
Usable Private Enclosed Adjoining,
Floor Area, Conference Corridor Occupiable
[ft.sup.2] Room Area, Area, Areas of
[ft.sup.2] [ft.sup.2] Interest,
1 1608 399 328 0
2 3281 361 263 0
3 4231 1000 375 0
4 6592 120 780 1120
5 7328 370 60 52
6 7625 850 775 2289
7 7747 400 94 0
8 8297 0 0 630
9 8329 445 0 414
10 8446 0 0 0
11 8493 1673 180 0
12 9329 1825 930 0
13 11,386 2050 1200 0
14 11,408 666 300 0
15 11,710 0 179 0
16 12,330 2412 0 1544
17 13,402 0 749 3245
18 14,177 809 0 347
19 14,898 1219 91 318
20 16,756 820 129 2632
21 20,972 1615 336 270
22 21,174 1578 132 576
23 21,970 1125 0 0
24 27,308 1155 0 309
25 30,750 1059 0 1136
26 34,127 1057 0 8073
27 39,595 1008 0 0
28 40,315 2345 2249 4196
29 45,781 1367 487 512
30 70,918 6927 2370 3441
31 100,614 7194 0 6690
Floor Plan Total Open Plan Total Private Total Number of
Workstation Office Area, Workstations
Area, [ft.sup.2] Present on Plan
1 0 550 5
2 1405 439 25
3 0 1056 8
4 2865 627 50
5 2281 1545 33
6 289 300 4
7 1700 1344 36
8 1872 1593 52
9 4193 580 90
10 2844 0 73
11 2800 780 55
12 1690 580 37
13 384 2125 16
14 1536 2120 41
15 3782 1712 78
16 4570 1556 116
17 2560 1972 58
18 3509 2475 119
19 6642 1016 93
20 2599 5092 65
21 7856 858 110
22 5712 600 214
23 1152 8320 40
24 7013 7275 140
25 4238 3912 115
26 1274 8423 90
27 13,063 4365 416
28 14,674 380 430
29 21,672 4608 416
30 21,856 2089 818
31 35,285 3518 995
Table 2. Floor Area–Calculated Values from Building Floor Plans
Floor Open Plan Private Total Common Area
Plan Usable Office Common Apportioned
Floor Space, Office to Open
Space, [ft.sup.2] Area, Plan,
[ft.sup.2] [ft.sup.2] [ft.sup.2]
1 0 693 331 0
2 1867 583 812 462
3 0 1838 1800 0
4 3426 750 1080 561
5 3880 2628 3020 1599
6 489 508 3122 200
7 3723 2943 4209 2023
8 3793 3227 4202 1921
9 6201 858 2698 2008
10 8446 0 5602 5602
11 4377 1219 3061 1577
12 3138 1077 4304 1448
13 759 4201 5627 375
14 3791 5233 6786 2255
15 7807 3533 6038 4025
16 5590 1903 2249 1020
17 4024 3099 4876 1464
18 6968 4914 7037 3459
19 10,656 1629 5612 4014
20 3863 7570 5485 1265
21 15,067 1646 10,037 7211
22 14,067 1478 12,576 8355
23 2388 17,249 11,373 1236
24 12,157 12,612 11,557 5145
25 12,598 11,627 20,405 8360
26 2,309 15,268 15,300 1035
27 28,055 9375 21,159 14,992
28 24,811 642 16,471 10,137
29 34,635 7364 17,135 12,963
30 42,253 4039 34,235 20,397
31 67,382 6718 47,928 32,097
Floor Common Area Common Common
Plan Apportioned Area Area
to Private Added to Added to
Offices, Open Private
[ft.sup.2] Plan as Offices
of Open Percent
1 143 26%
2 144 33% 33%
3 782 74%
4 123 20% 20%
5 1083 70% 70%
6 208 69% 69%
7 1599 119% 119%
8 1634 103% 103%
9 278 48% 48%
10 0 197%
11 439 56% 56%
12 497 86% 86%
13 2076 98% 98%
14 3113 147% 147%
15 1822 106% 106%
16 347 22% 22%
17 1128 57% 57%
18 2439 99% 99%
19 614 60% 60%
20 2478 49% 49%
21 788 92% 92%
22 878 146% 146%
23 8929 107% 107%
24 5337 73% 73%
25 7716 197% 197%
26 6845 81% 81%
27 5010 115% 115%
28 262 69% 69%
29 2756 60% 60%
30 1950 93% 93%
31 3200 91% 91%
Equation 3 calculates the apportioned common area as percent of open plan or private office.
Common area percent added = Common area apportioned to open plan or private office/Total open plan or private office workstation area (3)
Additional floor plans with insufficient data were analyzed but are not included here.
For each building floor plan, the floor area (i.e., footprint) of each workstation was determined. For open plan workstations, the floor area was defined as the area of the overall dimensions of the extent of the workstation in plan view (i.e., viewed from the ceiling) and is shown in Figure 3. For private office workstations (private offices with floor-to-ceiling walls) the floor area was defined as the floor area of the office enclosing the workstation and is shown in Figure 4.
Determination of Office Furniture Workstation Emitting Surface Area [A.sub.0]
As with workstation sizes in new buildings, the authors could not identify existing research that provided detailed dimensions of newly installed office workstation furniture to allow analysis of the furniture surface area present. Therefore, this study included determining the potential emitting surface areas (i.e., total of all major surface areas) of the workstations present on the office building floor plans analyzed.
Because ASHRAE 62.1-2004 was determined to be the most stringent and current standard to determine the minimum required outdoor, clean airflow rate [Q.sub.0] and neither larger nor smaller workstations necessarily represent a “worst-case” emissions condition under ASHRAE 62.1-2004, the 50th percentile workstation size was selected as most closely representing actual office conditions for more buildings. As total workstation surface area varies within workstations of identical floor area and more surface area increases the potential for higher concentrations, the 90th percentile conditions for total furniture surface area within the 50th percentile workstation footprint sizes were chosen to provide a representative “worst-case” office environment.
For the purposes of this study, total workstation surface area is defined as the sum of vertical panel surface area, horizontal work surface area, and storage external surface area. Using 90th percentile conditions for total workstation surface area aligns with current office furniture emissions requirements, which specify criteria based on whole workstations (USGBC 2004; Greenguard 2001; BIFMA 2005; SCS 2005). Determining emissions criteria for subsets of total workstation surface area (i.e., work surface, panel surface, storage surfaces, etc.) is a desirable goal. However, given the varied emission properties of the many materials used in office furniture, no combination of percentages of panel surface, work surface, and storage surface area constitutes an obvious “worst-case” situation for all materials. Therefore, to define a standardized office workstation, the average combination of panel, work surface, and storage surface areas as a percentage of total workstation surface area were chosen from workstations with the 50th percentile workstation footprint.
To determine vertical panel surface area, both faces of furniture system panels (i.e., partitions or screens) are included, edges are ignored, and all panel surface is assumed to be exposed. All panels present on each floor plan are included, even if they are part of a shared space or open plan conference area. For freestanding (i.e., non-panel-supported) furniture with desks and casegoods (i.e., modular cabinets), panel surface area is defined to include modesty panels, desk screens, gables, and end panels of desks or return units.
To determine work surface area, both the top and bottom of work surfaces are included, edges are ignored, and all surfaces are treated as exposed. All work surfaces and conference tables located within the office area, including in the office common area, are included.
To determine storage external surface area, all six surfaces (i.e., top, bottom, front, back, and two sides) are treated as exposed for flipper door overhead cabinets, storage cabinets, wardrobe cabinets, drawer pedestal files not located under a work surface, and lateral files not located under a work surface. For drawer-pedestal or lateral files located beneath a work surface, five surfaces (i.e., bottom, front, back, and two sides) are included (this excludes the top surface, as it is created by the work surface). For credenzas and freestanding two-drawer lateral files, their top surfaces are counted as work surface, not as external storage area, to allow for comparisons of usable work surface between workstation sizes and configurations. For shelves, the total horizontal surface area (i.e., top and bottom) is included, but edges, end panel structures, or supports are excluded for consistency. All storage within the office area perimeter, including shared banks of files in aisles, is included.
Based on this analysis (see Figure 3), for new open plan workstations the 50th percentile workstation floor area size is 3.34 [m.sup.2] (36 [ft.sup.2]). To investigate if the largest building floor plans with the most workstations analyzed were inappropriately influencing the distribution of workstation size, the data set was reanalyzed while excluding the two largest floor plans, but the results still showed the highest percentage of workstations were in the range from 2.97 to 3.72 [m.sup.2] (32 to 40 [ft.sup.2]). To include a reasonable sample of workstations in the determination of the 90th percentile total workstation surface area, all of the workstations with floor areas within plus or minus one-third of the standard deviation of the distribution were included. This equated to 36[+ or -]6.4 [ft.sup.2], which included open plan workstations with floor area in the range from 29.6 to 42.4 [ft.sup.2]. For new private office workstations the 50th percentile workstation floor area is 13.47 [m.sup.2] (145 [ft.sup.2]) and 1/3 standard deviation is 2.1 [m.sup.2] (23 [ft.sup.2]). Applying the same logic, private office workstations with floor areas between 11.3 and 15.6 [m.sup.2] (122 and 168 [ft.sup.2]) were included in the calculation for 90th percentile total workstation surface area. This resulted in a total of 1982 open plan workstations and 142 private offices from which 90th percentile total workstation surface areas were calculated.
To determine the floor area of associated common office space for each workstation, the apportioned common area as percent of open plan or private office (see Equation 3 and Table 2) from each floor plan was used as shown in Equation 4, below.
Equation 4 calculates workstation size (floor area) with apportioned common area:
Workstatiin size with common area = Workstation size x (1 + Common area percent added) (4)
Open plan workstations share furniture system panels (i.e., partitions or screens) between workstations in clusters (i.e., four, six, and eight packs of workstations); therefore, including both sides of panels when determining panel surface area of individual workstations overstates the actual amount of panel surface area per workstation, as recognized by some furniture emissions requirements (California 2000; BIFMA 2005; California 2006) and is shown in Figure 5.
Therefore, any of the individual workstation panel surface areas that did not take panel sharing into account were corrected by multiplying the overstated panel surface area for the individual workstation by the ratio of the total actual panel surface area, divided by the overstated panel surface area within the open plan area of each floor plan. For example, the California (2006) tiled workstation individually has 319 [ft.sup.2] of panel surface area but only 220 [ft.sup.2] of panel area when used in a six pack. The ratio of actual to overstated area is 220/319 = 69%.
The surface area of all furniture present in the office common space of each floor plan was also recorded and, just as common office floor area was apportioned to each workstation, the panel, work surface, and storage surface area present in the common office area was also apportioned to each workstation. For the open plan workstations within the 50th percentile size range specified, there was no panel surface area present in the common office space. For the private office workstations within the 50th percentile size range specified there was no additional panel, work surface, or storage area present in the common office space. The resulting 90th percentile, representative “worst case” standard workstation surface areas are noted in Table 3.
Table 3. Standard Workstation Surface Areas [A.sub.0]
Workstation Panel Area Work Surface Storage Total
System Type Area Total Workstation
Open plan 11.08 6.103 4.569 21.76
[m.sup.2] [m.sup.2] [m.sup.2] [m.sup.2]
(119.3 (65.69 (49.18 (234.2
[ft.sup.2]) [ft.sup.2]) [ft.sup.2]) [ft.sup.2])
Private 7.633 6.734 10.55 24.92
office [m.sup.2] [m.sup.2] [m.sup.2] [m.sup.2]
(82.16 (72.48 (113.6 (268.3
[ft.sup.2]) [ft.sup.2]) [ft.sup.2]) [ft.sup.2])
A wide range of office furniture workstation types can meet these area targets as documented in Appendix 2 of BIFMA M7.1-2005. The supporting data for the open plan workstations and private offices are shown in Table 4 and Table 5. For the open plan workstations within the 50th percentile range, the weighted average floor area with apportioned common space is 63.48 [ft.sup.2]. Therefore 64 [ft.sup.2] was chosen as the floor area for a standard workstation with a 36 [ft.sup.2] footprint with associated common space. For the private offices within the 50th percentile range, the weighted average floor area with apportioned common space is 253.22 [ft.sup.2]. Therefore, 256 [ft.sup.2] was chosen as the floor area for a standard private office workstation with a 144 [ft.sup.2] footprint with associated common space.
Table 4. Open Plan Workstations with 50th Percentile Floor Area
Workstation Quantity of Floor Area of Floor Area
ID Workstations Single of Single
on Plan Workstation, Workstation
[ft.sup.2] with Share
22 pd17 1 42.25 104.0
18 op7 2 36 71.6
16 op4 2 39 47.6
16 op3 3 39 47.6
28 sh2 4 37.5 63.4
16 op5 4 39 47.6
10 cl4 4 39 46.7
19 sh 4 40.5 65.0
30 op5 8 36 69.5
18 op2 9 33 65.7
10 cl8 24 39 46.7
31 op2 39 39 74.5
10 cl10 40 39 46.7
16 op2 42 39 47.6
16 op1 56 39 47.6
18 op3 67 36 71.6
29 sh 114 32 51.2
27 op1 253 35 75.2
28 ca 372 30 50.7
31 op1 934 36 68.8
Workstation Panel Area Panel Area Work Surface Work Surface
ID of Single of Single Area of Area of
Workstation Workstation Single Single
OVER STATED, Corrected Workstation, Workstation
Does Not for Panel [ft.sup.2] with Common
Include Sharing, Space,
Panel [ft.sup.2] [ft.sup.2]
22 pd17 72.85 40.90 47.93 47.9
18 op7 150.6 101.54 58.2 60.6
16 op4 n/a 118.70 38.90 38.9
16 op3 n/a 109.30 38.90 38.9
28 sh2 13.5 8.36 42.5 42.5
16 op5 n/a 84.70 38.90 38.9
10 cl4 129.50 79.16 48.87 53.2
19 sh 181.5 72.30 30.0 30.9
30 op5 130.0 129.52 41.0 41.0
18 op2 161.2 108.68 40.2 42.6
10 cl8 129.50 79.16 48.87 53.2
31 op2 346 233.12 45 45.1
10 cl10 129.50 79.16 48.87 53.2
16 op2 n/a 84.70 38.90 38.9
16 op1 n/a 72.20 38.90 38.9
18 op3 188.7 127.22 42.2 44.6
29 sh 104.5 62.23 32.475 32.9
27 op1 153.0 97.10 49.0 49.7
28 ca 98 60.52 35.8 35.8
31 op1 105 70.75 41 41.1
Workstation Storage Storage Total
ID External Surface Area Emitting
Surface Area of Single Surface
of Single Workstation Area–WITH
Workstation, with Common Common
[ft.sup.2] Space, Contents,
22 pd17 127.67 127.7 216.5
18 op7 38.9 62.4 224.5
16 op4 110.99 153.6 311.2
16 op3 110.99 153.6 301.8
28 sh2 71.6 85.1 136.0
16 op5 110.99 153.6 277.2
10 cl4 37.67 90.2 222.6
19 sh 60.2 67.5 170.8
30 op5 72.6 73.5 244.1
18 op2 38.9 62.4 213.7
10 cl8 37.67 90.2 222.6
31 op2 29.5 30.1 308.3
10 cl10 37.67 90.2 222.6
16 op2 110.99 153.6 277.2
16 op1 110.99 153.6 264.7
18 op3 38.9 62.4 234.2
29 sh 40.7 47.9 143.1
27 op1 41.9 41.9 188.7
28 ca 16.9 30.3 126.7
31 op1 14.8 15.4 127.2
Table 5. Private Offices with 50th Percentile Floor Area
Workstation Quantity of Floor Area of Floor Area Panel Area of
ID Workstations Single of Single Single
on Plan Workstation, Workstation Workstation,
[ft.sup.2] with Shared [ft.sup.2]
8 pmgra 12 122.5 248.22 60
8 pmgrb 1 122.5 248.22 60
18 p1 3 125 248.20 39.8
30 p7 1 125 241.66 146.7
24 p1spv 27 129 223.64 113.2
17 p1821 1 129.38 203.38 128.65
17 p1830 1 129.38 203.38 129.38
11 pmgrc 1 132 206.36 40
3 p1fin 8 132 229.74 82.5
7 p2 1 132 289.05 98.7
17 p1851 1 132 207.50 126.32
17 p1823 1 132 207.50 128.65
18 p2 3 140 277.99 39.8
21 p1 6 143 274.26 0.00
17 p1837 1 144 226.37 128.65
9 pmgr 4 145 214.46 20
2 p2 1 145 192.71 102.0
28 pdir 1 155 262.07 129.1
26 pass 41 160 290.02 63.55
20 p610 17 161 239.35 69.42
20 p624 9 168 249.75 69.42
30 p1 1 168 324.79 109.2
Workstation ID WorkSurface Area Storage External Total Emitting
of Single Surface Area of Surface Area,
Workstation, Single [ft.sup.2]
8 pmgra 32.75 74.6 167.4
8 pmgrb 32.75 74.6 167.4
18 p1 69.5 54.1 163.3
30 p7 66.8 131.0 344.4
24 p1spv 27.5 95.2 235.9
17 p1821 55.10 177.71 361.5
17 p1830 55.63 177.71 362.7
11 pmgrc 25 74.6 139.6
3 p1fin 60.0 120.5 263.0
7 p2 63.9 111.3 273.8
17 p1851 55.63 116.53 298.5
17 p1823 55.63 177.71 362.0
18 p2 69.5 54.1 163.3
21 p1 91.60 101.47 193.1
17 p1837 55.63 177.71 362.0
9 pmgr 32.8 74.6 127.4
2 p2 70.0 294.2 466.2
28 pdir 96.9 106.8 332.8
26 pass 85.83 94.77 244.1
20 p610 81.83 117.01 268.3
20 p624 81.83 117.01 268.3
30 p1 73.8 135.7 318.7
COMPARISON TO EXISTING OFFICE ENVIRONMENT MODELS
To facilitate a comparison to historical office environment models, the chamber test results for panel, work surface, and storage components of two example open plan workstations are provided in Table 6. Note the storage components are constructed of powder-coated metal that is extremely low emitting for formaldehyde.
Table 6. Formaldehyde Emission Factors of Open Plan Workstation
Open Plan Panel Emission Work Surface Storage
Workstation Factor, Emission Factor, Emission Factor,
ug/[m.sup.2]*h ug/[m.sup.2]*h ug/[m.sup.2]*h
1 50 100 Not detected.
2 50 15 Not detected.
Estimated formaldehyde concentrations for these two example open plan workstations using each office environment model are shown in Table 7. These models use a variety of different parameters and assumptions, and most do not use airflow rates based on ASHRAE 62.1-2004. Of course, other materials and combinations could produce different concentrations.
Table 7. Office Environment Models Comparison *
Parameters WA 1989 EPA 1996 CA 2000 BIFMA 2003
Workstation 8.92 – 12.08 12.08
Modeled space 25.5 25.7 33.0 33.0
Modeled 15.0 15.1 9.8 19.5
Modeled 1.0 1.0 0.5 1.0
Q0, modeled 25.49 25.70 16.57 33.00
Panel area 26.26 25.33 20.13 20.13
Airflow 0.97 1.01 0.82 1.64
Work surface 9.40 6.75 5.57 5.57
Airflow 2.71 3.81 2.97 5.92
Storage area 7.20 8.53 8.59 8.59
Airflow 3.54 3.01 1.93 3.84
Total-surface 42.9 40.6 34.3 34.3
Workstation 1 72.06 61.59 76.95 38.63
Workstation 2 46.50 43.38 53.64 27.03
Parameters Greenguard CA 2006 BIFMA 2005
Workstation footprint and 13.27 12.08 5.95
common area ([m.sup.2])
Modeled space volume 32.0 33.0 16.3
Modeled airflow rate 15.2 12.0 8.8
Modeled airflow rate 0.8 0.6 0.9
Q0, modeled airflow rate 25.60 21.00 15.02
Panel area ([m.sup.2]) 23.88 20.44 11.08
Airflow rate/panel surface 1.07 1.03 1.36
Work surface area 6.38 5.27 6.10
Airflow rate/work surface 4.01 3.99 2.46
Storage area ([m.sup.2]) 10.64 12.54 4.57
Airflow rate/storage 2.41 1.67 3.29
Total-surface area 40.9 38.2 21.8
Workstation 1 Formaldehyde 58.32 60.10 63.19
Workstation 2 Formaldehyde 41.05 42.73 35.04
* Model criteria for the BIFMA M7.1-2005 open plan workstation, the GEI
(Greenguard Environmental Institute) panel-based workstation, and the
California (2006) tile-based panel workstation were used. Accessories
(e.g., keyboard trays, lighting, tackboards, etc.) and sink effects
were not included. As of March 2007, GEI and the State of California
have updated model parameters that due to time constraints are not
included here. As stated earlier, the California model parameters
have been updated to utilize those of the BIFMA M7.1 test method.
These two example workstations illustrate that for workstation materials with known emission factors, each model will predict different concentrations (e.g., a work surface construction with a formaldehyde emission factor of 100 ug/[m.sup.2]?h determined from chamber testing will produce very different predicted concentrations depending upon which office environment model is used). The lack of uniformity between office environment models demonstrates the difficulty in comparing results across various programs and highlights the need for a standard model.
Table 4. Open Plan Workstations with 50th Percentile Floor Area
As total workstation emission concentrations are a combination of the various materials used (i.e., panel, storage, and work surface), no model predicts the highest concentration for all situations. But the ratios of airflow to surface area provide a relative indication of each model’s stringency (lower ratios are more stringent) for each surface type (panel, work surface, or storage). Referring to Equation 1, for a maximum allowable concentration (C), the maximum allowable emission factor (E) is equal to the allowed concentration multiplied by the ratio of airflow ([Q.sub.0]) divided by surface area ([A.sub.0]). Therefore, a lower ratio of airflow rate to surface area requires a lower emission factor. Based on this analysis, the California 2000 model is the most stringent for panel surface emissions with a ratio of 0.82, the BIFMA M7.1-2005 model is the most stringent for work surface emissions with a ratio of 2.46, and the California 2006 tiled workstation model is the most stringent for emissions from storage components with a ratio of 1.67 (highlighted in bold in Table 7.).
The representative, “worst case” standard open plan office environment for a single workstation system is defined as 5.94 [m.sup.2] (64 [ft.sup.2]) floor area by 2.74 m (9 ft) high (576 [ft.sup.3] or 16.3 [m.sup.3]), accounting for a standard 1.83 X 1.83 m (6 X 6 ft) open plan workstation system, traffic area, and support space for shared copiers, files, storage, etc. The space is assumed to be occupied by a single occupant and has an outdoor, clean air ventilation rate of 4.17 L/s (8.84 cfm) in accord with ASHRAE Standard 62.1-2004.
The representative, “worst case” standard private office environment for a single workstation system is defined as 23.78 [m.sup.2] (256 [ft.sup.2]) floor area by 2.74 m (9 ft) high (2304 [ft.sup.3] or 65.2 [m.sup.3]), accounting for a standard 13.38 [m.sup.2] (144 [ft.sup.2]) private office workstation system, traffic area, and support space for shared copiers, files, storage, etc. The space is assumed to be occupied by a single occupant and has an outdoor or clean air ventilation rate of 9.63 L/s (20.4 cfm) in accord with ASHRAE Standard 62.1-2004.
The office environments established from this study incorporate the well-documented trend to smaller workstation sizes, include a conservatively high (90th percentile) amount of total furniture surface, and utilize the minimum amount of outdoor, clean airflow rate in accord with the latest (2004) ASHRAE requirements. These office environments are in some cases more stringent than other historical models, are clearly based on actual buildings, and represent a “worst case” condition for current office furniture settings.
Ideally all office furniture emission programs should use the same occupant exposure scenarios to allow direct comparison of chamber test results across furniture types, manufacturers, and certification programs.
The authors gratefully acknowledge the hard work and analysis participation of the following individuals: Chris De Man, Steven Deer, Melissa Dubuis, Jon Gayhart, Robert Gelushia, Jim Thompson-Goodchild, David Hernandez, Doug Hietkamp, Jeff Musculus, Zabrina Pendon, Randy Ruster,
John Shank, Steve Trinkel, Denise Van Valkenburg, and Karen Worthy. Al Hodgson of Berkeley Analytical Associates provided the insight to compare airflow/surface ratios between exposure models. The authors also recognize the support, participation, and cooperation of the following corporations: Global Group International, Haworth Inc., Herman Miller Inc., Kimball International Inc., KI, Steelcase Inc., and Teknion Corporation.
ASHRAE. 2001. ANSI/ASHRAE Standard 62.1-2001, Ventilation for Acceptable Indoor Air Quality. Atlanta: American Society for Heating, Refrigerating and Air-Conditioning Engineers, Inc.
ASHRAE. 2004. ANSI/ASHRAE Standard 62.1-2004, Ventilation for Acceptable Indoor Air Quality. Atlanta: American Society for Heating, Refrigerating and Air-Conditioning Engineers, Inc.
ASTM. ASTM E1836-01, Standard Classification for Building Floor Area Measurements for Facility Management. West Conshohocken, PA: American Society for Testing and Materials.
BIFMA. 2003. BIFMA WP7.1-2003, White Paper on Office Furniture, Test Protocol for Emissions of Formaldehyde, Total Aldehydes, and TVOCs. Grand Rapids, MI: Business and Institutional Furniture Manufacturers Association International.
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BIFMA. 2005b. BIFMA X7.1-2005, Standard for Formaldehyde and TVOC Emissions of Low-emitting Office Furniture Systems and Seating. Grand Rapids, MI: Business and Institutional Furniture Manufacturers Association International. www.bifma.org/documents/X71_ 2005_ 1Sep05.pdf.
BOMA. 1996. ANSI/BOMA Z65.1-1996, Standard Method for Measuring Floor Area in Office Buildings. Washington, DC: Building Owners and Managers Association International.
California. 2000. Final environmental specifications to be included in the bid documents for office furniture systems, State of California, Department of General Services, Procurement Division. www.dhs.ca.gov/ps/deodc/ ehlb/iaq/VOCS/workstation.pdf.
California. 2004. California 01350, Standard Practice for the Testing of Volatile Organic Emissions from Various Sources Using Small-Scale Environmental Chambers (supersedes previous versions of small-scale environmental chamber testing portion of California Specification 01350), July 15, www.dhs.ca.gov/ps/deodc/ehlb/ iaq/VOCS/Practice.htm. (4)
California. 2006. State of California Bid Specification 7195-06BS-001, Open Office Panel System, Section A, Indoor Air Quality-VOC Emissions, February, Department of General Services, Procurement Division, West Sacramento, CA. www.cscr.dgs.ca.gov/ads/contract_ad_ detail.asp?AdNbr=A42452.
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Randal D. Carter
Associate Member ASHRAE
Jianshun S. Zhang, PhD
R. D. Carter is a principal engineer in the Codes & Approvals Department of Steelcase Inc, Grand Rapids, MI, and is chair of the Furniture Emissions Standard (FES) Subcommittee, Business and Institutional Furniture Manufacturers Association (BIFMA) International, Grand Rapids, MI, USA. J. S. Zhang is a professor and director of the Building Energy and Environmental Systems Laboratory, Department of Mechanical and Aerospace Engineering, Syracuse University, Syracuse, NY, USA.
(1) BIFMA is a not-for-profit trade association of furniture manufacturers and suppliers working together in a cooperative forum on issues of common concern. BIFMA has been an American National Standards Institute (ANSI) accredited standards developer for over 20 years and currently maintains eight voluntary American National Standards for furniture. Additional detail is available at www.bifma.org.
(2) As of March 2007, BIFMA was nearing completion of formal ANSI approval of the BIFMA furniture emissions standards.
(3) Additional guidance regarding the practical application of the ICC International Mechanical Code requirements for outdoor, clean air ventilation rates is available in the book, 2003 IMC Fundamentals, also available from the International Code Council.
(4) Although the California 01350 protocol was originally developed in 1998 for small chamber testing of building materials and later appended in 2004, the California Department of Health Services in 2000 and in 2006 wrote purchase specifications referencing 01350 for office furniture materials with results being used to estimate the emissions from whole workstation components or a whole workstation system.
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