Ventilation and Sustainable Laboratories
How Industrial Hygienists Can Influence Laboratories’ Effects on Environment and Climate
BY BRIAN SCHMIDT AND ANDREA GUYTINGCO
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As we’ve become increasingly aware of the impact our activities have on our planet, it is obvious that we need to manage the challenges of climate change as much as we do the health of people. A meta-analysis of more than 50,000 scientific articles on the topic of climate change published recently in the Bulletin of Science, Technology & Society revealed a startling finding: 99 percent of scientific papers published between the early 1990s and today agree that the current unprecedented rate of climate change is caused by humans. With this knowledge, responsible global enterprises are asking a simple question: how can we make our business more sustainable? The answer plays out in the form of ambitious multi-year strategies that aim to meet sustainability targets such as the reduction of waste, water consumption, and carbon footprint; adoption of green technologies and energy sources; and detailed reviews of product life cycles to reduce or eliminate environmental impacts at the earliest stages of product development. Leading organizations are already carbon neutral, or offsetting current emissions, with many aiming to become carbon zero—that is, to emit no carbon dioxide from operations—in the future. How can the modern industrial hygienist contribute to such sustainability initiatives?
One opportunity may be found in optimizing ventilation control strategies in laboratories. The suite of exposure control measures employed in laboratories is as familiar to IHs as James Reason’s Swiss cheese model or the hierarchy of controls. Decades of experience and testing have shown that measures from the standard use of laboratory overcoats, safety glasses, and closed footwear to fume hoods and general mechanical ventilation are effective if implemented and well maintained. In particular, ventilation—an essential part of any laboratory exposure control program—may provide an opportunity for IHs to help positively influence the impact of laboratories on the environment and climate change. A sustainable laboratory is one in which ventilation systems are calibrated to achieve both worker and environmental protection.
LABORATORY VENTILATION
According to a paper published in 2009 in the Journal of Chemical Health & Safety, general ventilation and the operation of fume hoods account for 60 to 70 percent of total energy costs associated with laboratories and therefore represent a significant opportunity for energy savings. While general office and building ventilation rates are typically informed by occupancy, it’s important to remember that laboratory ventilation requirements must also consider the health hazards present and ensure the control of accumulation or migration of airborne chemical hazards generated in laboratories (for example, particulates, gases, vapors, and aerosolized biohazards).
Fume hoods are integral to laboratories as a form of local exhaust ventilation intended to be the primary control of exposure to hazardous substances. Their operation is well defined in many countries by guidance addressing aspects such as basic design, air volume, face velocity, sash operation, alarm systems, maintenance, and testing. Advances that have the potential to improve the energy efficiency of fume hoods include variable air volume designs, which adjust face velocity based on sash height, or high-performance fume hoods, which rely on a combination of laminar airflow and reduced face velocities to reduce energy consumption.
While fume hoods contribute to laboratories’ overall energy usage, this article focuses on general ventilation requirements in laboratories. Due to the widespread use of fume hoods, general ventilation may be considered a secondary layer of ventilation control, diluting hazardous substance concentrations in the event of spills or other emissions from laboratory activities. General ventilation is also critical in terms of supplying sufficient fresh, breathable air to occupants; managing heat loads generated by equipment; maintaining room-to-room pressure differentials for the purposes of worker or product protection; and controlling air temperatures and relative humidity.
GENERAL VENTILATION REQUIREMENTS
Whereas fume hood requirements are readily available and well understood, firm requirements for general ventilation rates in laboratories are difficult to find. Even biosafety levels commonly associated with biological agents based on their risk group classifications do not specify minimum general ventilation rates for laboratory settings. Regulatory bodies and professional life science or engineering organizations often reference ventilation rates that are “typically” found or “normally adequate.” These “typical” air change rates are often between four and 12 air changes per hour (ACH). An examination of typical ventilation rates within our own company revealed that many laboratories operate toward the higher end of this range. Anecdotally, this may also be the case more generally in industry, academia, and wherever laboratories are found. Table 1 provides a summary of reference ventilation rates from a non-exhaustive list of organizations.
Table 1. Summary of Reference Ventilation Rates for Occupied Laboratories
Click or tap on the table to open a larger version in your browser.
Several organizations emphasize the importance of risk assessment in determining requirements for general ventilation. ACGIH, for example, offers no typical or recommended air change rates, stating in the 29th edition of Industrial Ventilation: A Manual of Recommended Practice for Design that “‘air changes per hour’ or ‘air changes per minute’ is a poor basis for ventilation criteria. The required ventilation depends on the generation rate and toxicity of the contaminant, not on the size of the room in which it occurs.” While we agree with this interpretation, general ventilation rates are nonetheless routinely expressed in air changes per hour.
In addition to the reference ventilation rates listed in Table 1, some European countries specify minimum required ventilation rates for laboratories. These requirements are typically expressed in cubic meters per hour based on occupancy levels or laboratory size, according to the European Committee for Standardization’s technical specification for ventilation systems in laboratories. This makes a direct comparison to ventilation rates presented in Table 1 difficult. Nonetheless, below are a few calculated examples expressed in terms of ACH as a reference point to standards in Europe. Assuming a laboratory with a floor area of 50 m2, a volume of 150 m3, and the presence of eight employees, the following indicative values can be calculated for selected European countries:
• Netherlands: 5 ACH (blanket requirement for all laboratories)
• Germany: 8 ACH (dependent on floor area)
• Spain: 4 ACH (dependent on occupancy)
Given the assumptions, these values generally fit within the ranges indicated in Table 1.
EXPOSURE RISK
Although chemical fume hoods are the primary engineering control for reducing exposure to hazardous substances in laboratories, general room ventilation plays an important role in minimizing the buildup of fugitive emissions, reducing odors, and evacuating spills and other accidental releases.
Peak airborne concentrations of hazardous contaminants may significantly affect the acute exposure of laboratory workers during spillage situations—for example, in situations where exposures could exceed short-term exposure limits. A study by Klein et al. published in 2009 in the Journal of Chemical Health & Safety examined the effect of different ventilation rates on the clearance of volatile organic compounds following spills. Though the study used a specific compound with a specific amount released (or spilled), it demonstrated that the peak concentrations generated may reasonably be expected to be around 40 percent higher at air change rates of 6 ACH compared to 8 ACH. For steady-state concentrations emitted from continuous activities like working on an open bench, the greatest relative improvements in chemical concentrations were seen at ventilation rates between 6 and 8 ACH. These experiments indicate that ventilation rates of 6 to 8 ACH may mark the lowest safe working range for many laboratories. Finally—and predictably—researchers observed longer clearance times at lower air change rates (for example, 60 minutes at 6 ACH compared to 10 to 15 minutes at 16 ACH).
Such data are valuable in understanding the role and impact of general ventilation as one part of an exposure control strategy. In addition, research has shown that a well-managed laboratory is free of airborne hazardous substances for up to 98 percent of its operational time (see the 2010 ASHRAE Journal article on demand-based control of laboratory air change rates under “Resources” below), indicating that spillage events or continuous release activities are rare when traditional control strategies are applied. However, Klein et al. recommend in a study published in 2009 in the Journal of Chemical Health & Safety that ventilation rates of less than 6 ACH should only be used for low-hazard laboratories and during unoccupied periods, regardless of control system.
Another point in question is the reduction of ventilation rates based on occupancy. While it may be generally expected that contaminant emissions would not occur during unoccupied periods, some laboratories run experiments or equipment continuously, which may give rise to emissions at any time. Low ventilation rates may further allow such emissions to build up during unoccupied periods, being cleared only when ventilation rates are increased based on occupancy. This could lead to inadvertent exposures among personnel during clearance periods, which could be up to an hour at typical ventilation rates, according to a 2019 article examining ventilation rates at university research laboratories.
ASHRAE LABORATORY VENTILATION DESIGN LEVELS
ASHRAE has proposed a structured qualitative hazard- and risk-based system to define laboratory ventilation design levels (LVDLs). The system, which is described in the ASHRAE publication Classification of Laboratory Ventilation Design Levels (PDF), is similar to chemical hazard and control banding systems in that it uses qualitative characteristics to assign laboratories to one of five design levels. These characteristics include the quantity of hazardous materials handled, the potential for airborne generation, and the severity of the hazard based on Globally Harmonized System of Classification and Labeling of Chemicals (GHS) classifications. Each LVDL is associated with several recommended design features, including recommendations for minimum air change rates.
ASHRAE’s LVDL system guides users toward selecting specific air change rates based on qualitative hazard and risk information within acceptable ranges. Application of the LVDL system would result in minimum ventilation rates between 2 and 8 ACH, depending on laboratory type, risk level, and occupancy. The LVDL system is an important reference as it introduces a framework by which assessors can adjust ventilation rates based on risk and perhaps opens assessors’ minds to considering ventilation rates as low as 2 ACH in low-risk, unoccupied laboratories.
Demand-based control systems allow for ventilation rates in laboratories to be adjusted based on central detection of contaminants.
DEMAND-BASED CONTROL VENTILATION SYSTEMS
Demand-based control (DBC) ventilation systems (or demand-controlled ventilation systems, as they are commonly known in the United States) may be key to creating modern sustainable laboratories. DBC systems allow for ventilation rates in laboratories to be adjusted based on central detection of contaminants; that is, ventilation is ramped up upon detection of airborne contaminants such as volatile organic compounds or particulates by dedicated sensor systems. Air is intermittently sampled at various locations in a laboratory and conveyed to a central detection bank consisting of particle detectors and a photoionization detector (PID). Such systems aim to solve many of the problems that might otherwise be associated with lowering ventilation rates (long clearance times in the event of spills, for example).
Particle counters associated with DBC systems can detect particles within a range of 0.3 to 2.5 microns (a subset of the respirable fraction), while PIDs can have detection limits as low as 0.025 parts per million (ppm) and an accuracy of ±0.2 ppm. In both cases, thresholds for increases in ventilation rate may be set by the laboratory manager, as described in the previously mentioned article about controlling ventilation rates at university research laboratories.
While DBC systems hold great promise, their implementation should be underpinned by a comprehensive assessment of laboratory hazards and exposure risk. For instance, DBC systems are not recommended to replace dedicated toxic, flammable, or oxygen-depleting gas alarm systems. In addition, some hazards are “invisible” to a DBC system based on the detection systems employed. For example, chemicals and gases have varying ionization potentials and specific PID lamps have a limited range. Where a central PID is used, a lamp should be selected that is appropriate to the types of hazards present in the laboratory. The same may be said of potential dust exposures where particle sizes (or a fraction of the powders being handled) have an aerodynamic diameter of more than 2.5 microns. Such limitations indicate why risk assessment is critical. Mixing and dilution dynamics in the laboratory space—as determined by air movement patterns and the relative placement of sensors—should also be considered if DBC systems are to be effective. (For example, a DBC system would not be able to respond effectively to an exposure event if air samples are taken in zones with comparatively poor mixing.) The two articles from the Journal of Chemical Health & Safety listed under “Resources” provide additional information on this topic.
Studies in laboratories utilizing DBC systems further inform our understanding of the relative importance of general ventilation as part of an exposure control strategy. One study focused on a cross-section of 18 different laboratory sites (mostly life-science and biology-related laboratories) using DBC systems indicated that no increased general ventilation was required for 99 percent of the study duration, which included 1.6 million operating hours. (A PDF of the study is available online.) While these data do not necessarily reflect conditions in all types of laboratories, the study’s findings demonstrate the potential for operating most any laboratory at reduced ventilation rates during specified timeframes. DBC ventilation systems promise tremendous energy savings by regulating ventilation rates; however, implementation should be carefully weighed against potential health and safety risks.
POTENTIAL SAVINGS
Potential energy savings are highly dependent on a plethora of factors. Examples include the total difference between air change rates for occupied and unoccupied spaces, setback time, duration, room volume, overall building size, and type of project (for example, retrofit versus a new build). In addition to making laboratories more sustainable, reductions in ventilation rates may also lead to significant cost savings. For reference, a 2018 study of hospital operating rooms indicated a 70-percent reduction in annual energy costs—equating to an energy savings of 3,827 megawatt hours (MWh)—by reducing the ventilation rate from 30 to 6 ACH while the rooms were not in use (see the study in the journal Environmental Monitoring and Assessment under “Resources”). In another example, the introduction of DBC ventilation systems in laboratory buildings at the University of California generated an energy savings of 16,831 MWh, which equates to approximately $2.3 million per year in energy cost savings (more information is available in a PDF of the case study).
TOWARD SUSTAINABILITY
Mechanical general ventilation in laboratories has long been established as an essential element of safeguarding the health, safety, and well-being of employees by providing sufficient fresh air, reducing the risk of fire or explosion, and helping to manage exposure risk resulting from the handling of hazardous substances. General ventilation rates for laboratories have historically been considered to be in the range of 4 to 12 ACH, despite limited published data justifying this range as appropriate—not to mention the lack of specific, mandatory regulatory requirements in this area.
Alongside the risk-based LVDL system offered by ASHRAE, demand-based control systems offer the promise of significant energy and cost savings, making laboratories more sustainable and efficient by regulating ventilation rates. Published data on the impact of air change rates on contaminant clearance and the limitations inherent to DBC sensor systems indicate that reductions below 6 ACH are likely best reserved for low-hazard laboratories and that implementation of these systems should always be underpinned by a comprehensive hazard and exposure risk assessment. Industrial hygienists have the ideal skill set and knowledge base to help organizations and clients assess the required ventilation rates to make laboratories more sustainable without sacrificing the protection of worker health.
BRIAN SCHMIDT, MSc OH, MSc Tox, CMFOH, is the global lead of industrial hygiene at Takeda Pharmaceuticals International AG in Switzerland.
ANDREA GUYTINGCO, MPH, CIH, is an environment, health and safety business partner at Takeda Pharmaceuticals in Cambridge, Massachusetts.
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Pandemic Readiness in Laboratories
During the COVID-19 pandemic, our understanding of transmission of the SARS-CoV-2 virus has expanded, putting different transmission routes into focus. A couple of years into the pandemic, the role of airborne transmission by the inhalation of very fine respiratory droplets and aerosol particles containing infectious virus has become more apparent, emphasizing the importance of good ventilation as barrier to disease spread. Laboratory designers should consider ventilation rates not only for mitigation during the current pandemic, but also in terms of future readiness.
An article published in JAMA in April 2021 suggests that air change rates of 4 to 6 ACH help reduce far-field airborne transmission of SARS-CoV-2 indoors if provided as fresh air and combined with filtration of at least MERV 13, which captures 98 percent of particles in the 3–10 µm range). These indicative ACH values align with the traditional risk-based suggestions discussed in this article.
RESOURCES
ACGIH: Industrial Ventilation: A Manual of Recommended Practice for Design, 29th ed. (2016).
The Air Conditioning, Heating, and Refrigeration News: “Controlling Ventilation Rates at University Research Laboratories” (2019).
Aircuity Case Study: “University of California, Irvine: Significant Energy Savings through Smart Lab Design and Demand Control Ventilation” (PDF, 2014).
Aircuity White Paper: “Laboratory Ventilation ACH Rates: Standards and Guidelines” (PDF, 2012).
American National Standards Institute (ANSI): ANSI/ASSP Z9.5, Laboratory Ventilation (2012).
ASHRAE: ANSI/ASHRAE Standard 62.1, Ventilation for Acceptable Indoor Air Quality (2019).
ASHRAE: ASHRAE Laboratory Design Guide: Planning and Operation of Laboratory HVAC Systems, 2nd ed. (2015).
ASHRAE: Classification of Laboratory Ventilation Design Levels (PDF, 2018).
ASHRAE Journal: “Demand-Based Control of Lab Air Change Rates” (PDF, 2010).
Bulletin of Science, Technology & Society: “The Consensus on Anthropogenic Global Warming Matters” (2016).
Environmental Monitoring and Assessment: “Effect of Ventilation Rate on Air Cleanliness and Energy Consumption in Operation Rooms at Rest” (2018).
European Committee for Standardization: CEN/TS 17441:2020, Laboratory Installations – Ventilation Systems in Laboratories (April 2020).
JAMA: “Indoor Air Changes and Potential Implications for SARS-CoV-2 Transmission” (April 2021).
Journal of Chemical Health & Safety: “Laboratory Air Quality and Room Ventilation Rates” (2009).
Journal of Chemical Health & Safety: “Laboratory Air Quality and Room Ventilation Rates: An Update“ (2011).
National Fire Protection Association: NFPA 45, Standard on Fire Protection for Laboratories Using Chemicals (2019).
National Research Council of the National Academies:
Prudent Practices in the Laboratory: Handling and Management of Chemical Hazards, Updated Version (2011).
Prudent Practices in the Laboratory: Handling and Management of Chemical Hazards, Updated Version (2011).
OSHA: Occupational Safety and Health Standards, Toxic and Hazardous Substances, Occupational Exposure to Hazardous Chemicals in Laboratories, Appendix A, National Research Council Recommendations Concerning Chemical Hygiene in Laboratories (Non-Mandatory).