Editor’s note: This three-part article is one of a series of Technical Bulletins and Best Practice Guides for laboratories, produced by Laboratories for the 21st Century (“Labs21”), a joint program of the U.S. Environmental Protection Agency and the U.S. Dept. of Energy. Geared toward architects, engineers and facility managers, these publications provide information about technologies and practices to use in designing, constructing and operating safe, sustainable highperformance laboratories. For more information about these free resources, see: www.Labs21century.gov/toolkit/bp_guide.htm. This article discusses standard practices in lab ventilation and an overview for preparing to optimize. Part two, to be published in March, will cover implementation strategies for optimization. Part three, in the April edition, will provide some case studies and comments regarding commissioning.

The Labs21 website also provides full information about the agency’s 2010 annual conference, to be held in Albuquerque, Sept. 28-30. The comeeting is sponsored by I²SL, the International Institute for Sustainable Laboratories.

Fig. 1. Annual electricity use in Louis Stokes Laboratory, National Institutes of Health, Bethesda, Md.

Laboratories are highly energy-intenive, often using four to six times more energy per ft² than a typical office buildng. Most existing labs can reduce their energy use by 30 to 50% with existing echnology, which is significant given heir $1 billion to $2 billion annual energy costs in the U.S. Nearly half of the electrical energy use in a typical laboratory can be attributed to ventilation, and reducing a laboratory’s ventilation needs can lower the cost of building and maintaining a facility (Fig. 1).

The objective of this Best Practice Guide is to help users optimize ventilation airflow and reduce associated energy use while maintaining or improving safety. While this guide highlights best-practice strategies focused on reducing energy use, it does not specify how to set a ventilation rate. Note that the terms “good” and “better” practices are used to describe options that improve standard practices.

Perspective: Standard practice
In standard laboratory-design practice, ventilation rates are usually derived from guidelines, presented as a range of values in design standards. When using a guideline to determine a ventilation rate for a laboratory, the highest value from the range is often chosen because the guidelines are highly generalized; however, designers should be cautious when using these wide-ranging recommendations. Design firms, or authorities having jurisdiction, typically use a guideline without questioning the true source and the reasoning behind its value. Similarly, designing by only referencing past efforts, by “what’s in the drawer,” limits energy efficiency and may even compromise safety.

Table 1. Common laboratory ventilation rate codes Table 1. Ventilation rate codes are not consistent.
Code	Ventilation rate	Comment
IBC-2004	1 CFM/ft2 for H-5	Section 415.9.2.6
IMC-2004	1 CFM/ft2	Rate required for storage areas that exceed maximum allowable quantities of hazardous materials. (Section 502.8.1.1.2)
UBC-1997	1 CFM/ft2 for H-6	Uniform codes have been replaced by international codes beginning in 2000. (Section 1202.2.5)

A simplified “more is better” design approach is not a substitute for due diligence. Ventilation guidelines should only be applied as their authors intended—as ranges, and not as absolutes.

Standard practice also entails the blanket adoption of ventilation guidelines as constant values, with the ventilation rate rarely being dynamically controlled or otherwise tailored to the occupancy or conditions of the site, or optimized for energy efficiency or safety. Some publications simply recommend 4 to 12 air changes per hour (ACH). The result can be excessive (or inadequate) ventilation for the lab in question, causing unnecessary energy expenditures. Facility owners also bear the consequences of requiring an unsubstantiated high ventilation rate, inadvertently forcing the engineer to design a potentially wasteful HVAC system.

Table 2. Common laboratory ventilation rate standards Table 2. A review of the standards applicable to air change rates and ventilation in labs.
Standard	ACH number	Comment
ANSI/AIHA Z9.5	The specific room ventilation rate shall be established or agreed upon by the owner or his/her designee.	The latest version of the American National Standards Institute and the American Industrial Hygiene Assn. standards (ANSI/AIHA Z9.5-2003, Section 2.1.2) states that a method based on "air changes per hour is not the appropriate concept for designing containment control systems. Contaminants should be controlled at the source." ANSI/AIHA also states that the ACH do not "reflect actual mixing factors" of a particular room.
NFPA-45-2004	Minimum 4 ACH unoccupied; "occupied"typically greater than 8 ACH."	According to the National Fire Protection Assn.'s Standard NFPA 45, Appendix A: A-8-3.5 (NFPA 45 2004), room air currents in the vicinity of fume hoods should be as low as possible, ideally less than 30% of the face velocity of the fume hood. Air supply diffusion devices should be as far away as possible from fume hoods and have low exit velocities.
AGGIH-Ind. Vent.-24th Ed.-2001	The requird ventilation depends on the generation rate and toxicity of the contaminant, not on the size of the room in which it occurs.	This standard from the American Conference of Governmental Industrial Hygienists states that "'Air changes per hour' or 'air changes per minute' is a poor basis for ventilation criteria where environmental control of hazards, heat and/or odors is required." The impact of the laboratory's ceiling height is identified as one reason why an air change approach does not adequately address the required contamination control (Section 7.5.1, Air Changes).
ASHRAE Lab Guide-2001	4-12	The ASHRAE Laboratory Design Guide includes suggestions relating to the following: Minimum supply air changes Minimum exhaust air changes Minimum outdoor air changes Recirculation considerations
OSHA 29 CFR Part 1910.1450	4-12	The Ocupational Safety and Health Administration specifies a room ventilation rate of 4 to 12 air changes per hour, which "is normally adequate general ventilation if local exhaust systems such as hoods are used as the primary method of control." This range is extremely broad and provides a designer with little guidance.

Ventilation codes and guidelines
After reviewing the user’s program, or design intent document, the project architect determines the laboratory’s occupancy classification. For this resolved occupancy classification, the ventilation rate is provided in a building code specified by the municipality or authority having jurisdiction.

The occupancy classification has a significant impact on a building’s energy use. For example, for particularly hazardous occupancy classifications, the ventilation rate is legally stipulated by the applicable building code. However, for less hazardous occupancies, design standards with a range of rates are used only as guidelines for ventilation rates. Note that a design standard may be adopted by the authority having jurisdiction as a “code” requirement.

In the case of building codes for hazardous classifications, ventilation rates are stipulated in terms of floor area as ft³ /min (CFM) per ft², while ventilation guidelines from building design standards for laboratories are based on the total volume of the space and expressed as ACH, which is how many times the entire air volume in the laboratory is replaced each hour.

Prevailing building codes and design standards provide a context in which best-practice strategies can be implemented. Consider the ventilation guideline provided by OSHA 29 CFR Part 1910.1450, which calls for a range of 4 to 12 ACH for a “laboratory” that often has an occupancy classification of “B.” In contrast, the International Building Code (IBC) (2004) calls for a rate of 1 CFM/ft² for an occupancy classification of H-5, which is considered to be a hazardous environment (see Table 1 for this and other examples). Note that for certain quantities of flammable liquids, these must be “used” in a “control area” in order for a building to have a “B” occupancy classification.

As an example of how a code’s ventilation rate (or ambiguity) influences energy use, consider the following two scenarios. One laboratory space, whose occupancy classification is IBC H-5, has a 10-ft-high ceiling and an exhaust airflow rate requirement of 1 CFM/ft²; the exhaust airflow from this lab will result in 6 ACH. However, another laboratory space, which has the same floor area but a 15-ft-high ceiling and a “B” occupancy classification, follows the OSHA guideline of 12 ACH and flows three times more air than the higher-hazard H-5 lab.

Applying fan-law energy calculations, the “B” lab will consume more than three times the energy of the “H-5” lab. In addition, the first cost of the H-5 lab’s smaller HVAC system will also be less. Note that even though the airflow rate per unit floor area eliminates ceiling height as a determinant of air change requirements, neither the volumetric ACH method nor the area-based CFM method predicts the effectiveness of the ventilation.

Codes and standards
Laboratory designers should study code requirements, understand each classification, be familiar with their potential energy impacts, and relate these findings to the project design team.

Table 1 lists typical design codes that are often used as ventilation-rate guidelines. Table 2 lists common design standards containing guidelines for a laboratory’s ventilation rate.

Standard practice: More is not necessarily better
While “rules of thumb” often dictate that “more is better”—i.e., that increased ventilation rates yield increased safety, worker comfort, and research productivity—real-world experience shows that this is not the case. In fact, excessive ventilation can diminish safety conditions in labs that use hazardous and odorous materials as part of their experimental studies. Thus, best practices optimize rather than maximize ventilation, and consider the “mixing factor” of the pollutant being removed from the lab.

Studies of laboratory facilities have demonstrated that the room air change rate has less effect than a room air-diffusing system or other ventilation characteristic on environmental conditions. Designers need specifications that are tailored to a laboratory’s air circulation arrangement, because many conventional design parameters and recommendations should not be universally applied; for example, they may not relate to microenvironmental (e.g., cage) conditions in a laboratory (Zhang et al., 1992; McDiarmid, 1988).

Other studies show that air dilution or replacement does not protect personnel from exposure to concentrated bursts of aerosols in biological laboratories. For example, Crane (1994) quotes Chatigny and West (1976), who say that "increasing ventilation rates from 6 to 30 air changes per hour (ACH) has a minimal effect on aerosol concentration of microorganizms in the first few minutes after release."

Adjusting ventilation is not the only way to control environmental conditions. For instance, Memarzadeh (1999) has shown that controlling the humidity in animal rooms is more effective than using high air change rates in managing the production of ammonia from animal urine. This has allowed users to decrease "the air change rate from 15 to as low as 5, while improving the welfare of the animals."

Preparation: Process overview
Determining a laboratory facility's ventilation rate is not an exact science; therfore, a "precise" answer cannot be the only goal of the ventilation system designer. More important is the process carried out by the ventilation system designer to resolve an appropriate ventilation rate. At the initial (conceptual) level, the designer should consider the following four-step process.

Step 1: Review design intent
Study and support the features embodied in the facility's design intent document. The document should include three main categories, which are followed by the designer's actions:

• User programming (characterize the building's mission, deffereniate between "needs" and "wants," evaluate client statements, list research goals).
• Occupancy classification (interpret municipality's building code, determine occumpancy classification requirements, analyze energy-use impacts, relate findings to the project design team).
• Essential building functions and systems (identify architectural features, evaluate engineering approaches, itemize main design elements and characteristics, determine "boundaries" for design).

Step 2: Identify authority having jurisdiction
Ensure that the authority is identified and involved, and has a clear understanding of the difference between codes and standards:

• Codes have “force of law,” are restrictive, and require compliance.
• Standards are open to interpretation, have a wide span of acceptable values, and are subject to manipulation. Adopted standards may be based on sound judgment, but could be biased or reflect entrenched doctrine; they may be archaic and not reflect the latest technology or practices.

Step 3: Assess priority and resources for optimizing ventilation rates

• Garner team support to optimize laboratory ventilation rate during a design charrette.
• All stakeholders identify the lab’s design goals and issues.
• Promote fundamental impact of lab’s ventilation rate on continuous safety performance, immediate HVAC first-cost, and long-term energy use.
• Consider the scope (owner’s priorities), schedule (available time) and budget (value engineering).

Step 4: Implement a design strategy.
Once steps 1 through 3 have been completed, implement the appropriate design strategy. A design strategy can be chosen from one of the following three options:

• Constrained design: Restricted, or constrained by building code.
• Standard design: Conventional practice that employs design standard’s guidelines.
• Optimized design: See following details. If an optimized design strategy is chosen, a design team’s support must balance scope, schedule and budget limitations with “attitude” and “resources.” The following should be considered by the design team.

Optimized design support requires a change in attitude:

• Do not impose standard or usual policies and methods.
• Willingly provide information on experimental procedures.
• Remain open and flexible to new ideas and alternate ways of doing science.

Optimized design support needs to be quantified:

• Use life-cycle costing as a measurement tool for decision making.
• Establish project schedule and project costs, and get designer’s concurrence.

Fig. 2. Process flow chart.

Ventilation dilution
The principal device used to contain harmful emissions from chemicals within a laboratory is the chemical fume hood. Such hoods come in various sizes, but a typical internal working surface dimension is 66 in. wide and 26 in. deep. If one assumes an 18-in. sash opening, and an average face velocity of approximately 100 fpm, approximately 850 cfm of air is induced through the hood by the laboratory exhaust system.

Furthermore, for hoods designed in accordance with the guidance provided in Appendix A.6.4.6, NFPA 45-2000, a minimum of 300 cfm of dilution air is admitted when the sash is fully closed. For laboratory ventilation systems designed in accordance with the guidance provided in Appendix A.6.3.5 of NFPA 45-2000, room air current velocities in the vicinity of the hood should ideally be less than 30 fpm.

Given the hood dimensions and ventilation system design guidance described above, consider an accidental 1-L spill of hydrogen fluoride or hydrogen chloride in the vicinity outside of the fume hood. In calculating the concentrations resulting from either of these spills, it can be shown that the contaminant threshold limit value IDLH—Immediately Dangerous to Life and Health—is exceeded regardless of sash position. Additional results are summarized below:

• If room air current velocities in the vicinity of a hood are increased above the minimum recommended level (as noted above), emission rates from the spill increase, as do the resulting concentration levels of contaminants in the air flowing toward the fume hood.
• If the volumetric airflow rate in the vicinity of the hood is increased, as in the case of opening the sash of a variable air volume (VAV) hood, lower concentration levels result.
• Unfortunately, ventilation airflow rates have to increase by at least one or two orders of magnitude above those induced through the fume hood to keep from exceeding lifethreatening threshold levels. Furthermore, ventilation systems designed to provide such airflow rates are impractical because they are physically constrained by the size of the building.
• Consequently, ventilation dilution is not the solution to pollution resulting from an accidental spill of hazardous chemicals within a laboratory.
• Finally, the above results point to the importance of handling chemicals safely before delivering them to chemical fume hoods. Note: IDLH was established by the National Institute for Occupational Safety and Health. It is defined as the concentration of airborne contaminant that poses a threat of death, immediate or delayed permanent adverse health effects, or effects that could prevent escape from such an environment.

Ventilation dilution section by John L. Peterson, PE, Office of Facilities Planning and Construction, Uniy. of Texas System

The upcoming March issue will present strategies for the optimization process.

The author of this guide was Geoffrey C. Bell, PE, M.Arch, from the Lawrence Berkeley National Laboratory, Berkeley, Calif. (GCBell@lbl.gov).

Contributors and reviewers were John Piatt, PE, Pacific Northwest Regional Laboratory, Richland, Wash.; John Peterson PE, Univ. of Texas System; Otto Van Geet, PE, National Renewable Energy Laboratory, Golden, Colo.; Paul Mathew, Lawrence Berkeley National Laboratory, Berkeley, Calif.; and Low DiBerardinis, Massachusetts Institute of Technology, Cambridge.

For general information on the Labs21 program, contact Dan Amon (amon.dan@epa.gov) or William Lintner (william.lintner@ee.doe.gov).

Full References List Associated with Article

• Barkley, W.E. “Issues in Laboratory Ventilation for Hazard Control,” Proceedings of the Symposium on Laboratory Ventilation Hazard Control (Frederick, MD, 1976).
• Bell, G.C., E. Mills, D. Sartor, D. Avery, M. Siminovitch and M.A. Piette. A Design Guide for Energy-Efficient Research Laboratories, LBNL-PUB-777, Lawrence Berkeley National Laboratory, Center for Building Science, Applications Team, September 1996–2003.
• Bell, G. “Retrocommissioning Laboratories for Energy Efficiency,” Laboratories for the 21st Century, Technical Bulletin, 2006.
• Crane, J.T. “Biological Laboratory Ventilation and Architectural and Mechanical Implications of Biological Safety Cabinet Selection, Location, and Venting,” ASHRAE Transactions, 100(1):1257–1265, 1994.
• Maghirang, R.G., G.L. Riskowski and L.L. Christianson. “Ventilation and Environmental Quality in Laboratory Animal Facilities,” ASHRAE Transactions, 102(2):186–194, 1996.
• Marshall, J.W. “Health Care Ventilation Standard: Air Changes per Hour or CFM/ Patient?” ASHRAE Journal, 38(9): 27–30, September 1996.
• McDiarmid, M.D. “A Quantitative Evaluation of Air Distribution in Full Scale Mock-Ups of Animal Holding Rooms.” ASHRAE Transactions, 94(1): 685–693, 1988. (This article also appears in Laboratory HVAC, 1995, 89–94, ISBN 1-883413-25-7.)
• Memarzadeh, F. “Of Mice, Men, & Research.” Engineered Systems, 16(4), April 1999.
• Mills, E., H. Friedman, T. Powell, N. Bourassa, D. Claridge, T. Haasl and M.A. Piette. The Cost-Effectiveness of Commercial-Buildings Commissioning: A Meta-Analysis of Energy and Non-Energy Impacts in Existing Buildings and New Construction in the United States. Lawrence Berkeley National Laboratory Report No. 56637, 2004.
• Riskowski, G.L., R.G. Maghirang and W. Wang. “Development of Ventilation Rates and Design Information for Laboratory Animal Facilities. Part 2 - Laboratory Tests.” ASHRAE Transactions, 102(2): 195–209, 1996.
• Zhang, Y., L.L. Christianson, G.L. Riskowski, B. Zhang, G. Taylor, H.W. Gonyou and P.C. Harrison. “A Survey of Laboratory Rat Environments.” ASHRAE Transactions, 98(2): 247–253, 1992.

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