As published in ASHRAE Journal, September 2023

Features and design for these laboratories are driven by the nature of the science being taught and the level of hands-on work by students. Understanding the curriculum is key. Figure 1 lists some typical lab-based science classes. Physics and geology typically present minimal hazards. Chemistry may present exposure risk depending on the grade level and associated curriculum. Biology labs may present biological hazards but are generally more benign than chemistry.

If dissections are used to teach anatomy, there may be an exposure risk if formaldehyde or other preservatives are used. Figure 2 shows relative hazard level of various science labs. In my company’s K – 12 practice, we are seeing increasingly sophisticated science labs in middle and high schools. Some approach the level of higher education teaching laboratories. Figure 3 lists some codes and standards that address laboratory spaces. Some do not apply to education applications; however, they provide valuable background information and may represent best practices.

Engineering and maker spaces are specialized science laboratories that may include a variety of activities that present risk. Maker spaces are hands-on learning environments that sometimes include metalworking, woodworking, welding, painting, additive manufacturing (3-D printing) and laser and plasma cutting. These activities require specialized exhaust and/or dust collection. These spaces will be covered in a future column.

Basics of Laboratory Hazards

Many hazards may be present in the laboratory. Figure 4 indicates hazards that may exist. It’s incumbent upon the design professionals to understand the hazards and design engineering controls to mitigate potential exposure—science teachers and professors may not have the background needed to do so.

The NFPA Diamond (Figure 5) is a useful tool for identifying and categorizing hazards. It identifies four categories of hazard by color and uses a numerical rating system to indicate the level of hazard. The numeric category ranges from 0 to 4, with 0 representing no hazard and 4 representing the highest hazard. Health hazards are identified with a blue diamond, fire hazards are identified with a red diamond and reactivity hazards are identified with a yellow diamond. A white diamond is used to identify specific hazards, such as acids, corrosives, radioactive, etc.

When designing science labs, it is important to obtain a list of all chemicals that will be used and review the material safety data sheets (MSDS) for each. These data sheets normally list the hazards and identify the NFPA rating for each hazard category. Designers should also understand how the chemicals will be used. Will they be used on an open bench? In the fume hood? Only in the prep room by the instructor? This understanding will then guide the design of engineering controls to minimize exposure risk.

Containment

Understanding the principle of containment is key to designing safe laboratories. Primary containment is the first line of defense against exposure and is typically the fume hood for hazardous chemicals and the biological safety cabinet for biological agents. Open use of materials that are hazardous to humans should always be done inside a primary containment device.

Secondary containment consists of the lab enclosure, general lab exhaust and keeping the lab pressure negative relative to the adjacent corridor. Best practice is always to keep the lab door closed to maintain secondary containment. Lab exhaust fans should run continuously unless all hazards are removed from the lab. ANSI/ASSP Standard Z9.5-2022, Laboratory Ventilation, requires that air move from lower to higher hazard. Air should always move from the corridor into the lab.

Fume Hoods and Biological Safety Cabinets

Primary containment devices should be selected carefully and should always be used as the first means of protection from exposure. There are many types of fume hoods and biological safety cabinets. Designers should familiarize themselves with these devices and understand how to apply them. The architect or lab planner typically specifies these along with the laboratory furnishings in Division 11 of the project specifications. However, in my experience, architects who design education facilities may not be familiar enough with these devices to apply them properly. I normally ask the architect if I can review the fume hood and/or biological safety cabinet specification, and they are almost always happy to have the assistance.

The location of fume hoods and biological safety cabinets must be carefully considered. They should be located away from doors and main traffic aisles. Doors and personnel movement can create cross drafts and may decrease a hood’s containment ability.^1,2 Supply diffusers should be located so as not to create a cross draft. Standard Z9.5 states that “Supply air distribution shall be designed to keep air jet velocities less than half, preferably less than one-third of the capture velocity or the face velocity of the laboratory chemical hoods at their face opening.”

Some activities, such as small dissections, may benefit from a point of use exhaust device, such as a snorkel in lieu of a fume hood. Snorkels have an articulating arm and can be positioned directly behind the operation to pull contaminants away from the student’s breathing zone.

Science Laboratory Exhaust

The International Mechanical Code (IMC) (2021 and previous versions) requires that science laboratories in education occupancies be mechanically exhausted at the rate of 1 cfm/ft² (5 L/s·m²). This air is not allowed to be recirculated to other spaces. In limited situations, recirculation of some air from laboratories is allowed, but this would only be allowed if the supply air to the space exceeds 1 cfm/ft² (5 L/s·m²) (see Note g in Table 403.3.1.1 of the 2018 IMC). If a science laboratory will not have any materials present that are hazardous to humans, it may be prudent to label it a “science classroom” to avoid the IMC exhaust requirement for science laboratories.

The Ventilation Rate Procedure in ANSI/ASHRAE Standard 62.1-2022 requires educational science laboratories to be exhausted at 1 cfm/ft² (5 L/s·m²) and designates the air as Class 2. Per the standard, Class 2 air may only be recirculated within the space of origin or to Class 2 or Class 3 spaces that are used for the same or similar purpose and involve the same or similar pollutant sources. The standard also states that exhaust from laboratory hoods shall be “air Class 4 unless determined otherwise by the EHS [environmental health and safety] professional responsible to the owner or to the owner’s designee.” The standard prohibits recirculation or transfer of Class 4 air. This appears to prohibit the use of any energy recovery device that has leakage or carryover from the exhaust to the supply side.

If fume hoods are present in the lab and their combined exhaust flow equals or exceeds 1 cfm/ft² (5 L/s·m²), they are allowed to count toward the code or ASHRAE Standard 62.1-2022 required exhaust. If the combined hood airflow is less than or will be reduced below 1 cfm/ft² (5 L/s·m²), additional general exhaust would be required to make up the difference.

Most higher education science laboratories are business (B) occupancy per the International Building Code; therefore, the science lab exhaust requirement in the IMC technically doesn’t apply since it only addresses education (E) occupancies. ASHRAE Standard 62.1-2022 uses the term “Occupancy Category” when defining exhaust requirements for educational science laboratories. It does not differentiate between code occupancy classifications, so the exhaust requirements in the standard would apply.

The IMC also lists requirements for location and termination point for exhaust ducts carrying flammable vapors, fumes or dusts. This may require the fan have a stack. Proximity to operable openings, exterior walls and roofs, and adjoining grade are all addressed.

An adequate supply of makeup air should be supplied to the lab either via supply or transfer air. Since Standard Z9.5 states that “airflow shall be from areas of low hazard to higher hazard,” airflow from the adjacent corridor should flow into the lab to minimize the risk of hazardous fumes migrating into the corridor or other adjacent spaces.

It may be prudent to check with the fire marshal associated with the authority having jurisdiction to confirm whether they have additional requirements that need to be addressed.

Eyewash and Shower

Where a person’s eyes or body may be exposed to injurious corrosive materials, such as a science lab, an emergency eyewash and shower is needed³ and should be installed. ANSI/ISEA Z358.1-2014, Standard for Emergency Eyewash and Shower Equipment, provides guidance for installation, minimum performance and use.

Separate fixtures or a combination unit can be used. The fixture must be located so occupants can reach it in 10 seconds or less, and the path to the fixture must not be hindered with obstructions. An appendix to the standard suggests 55 ft (17 m) maximum as the distance that can be covered in 10 seconds. A door is considered an obstruction. Therefore, if corrosives are used, the fixture must be in the same room as the hazard.

Flushing water must be “tepid,” which is defined as 60°F – 100°F (16°C – 38°C). This may dictate the need for domestic hot water service at the equipment and a thermostatic mixing valve to ensure the water is delivered within the required temperature range. Most emergency fixtures offer an option for an onboard thermostatic mixing valve.

In general, floor drains in laboratories using hazardous chemicals should be avoided due to the possibility of introducing spilled chemicals into the sanitary sewer system. This presents a dilemma regarding the emergency eyewash and shower. Per Standard Z358.1, an emergency shower must be capable of discharging 20 gallons/min (1.2 L/s) of water for 15 minutes. A shower operated for 15 minutes would result in 300 gallons (1136 L) of water being dumped into the lab! This would certainly flood the lab, surrounding spaces and floors below. Even if a floor drain were below the shower, it would not be able to accept this amount of water and would likely flood the building. Cleanup with a shop vacuum and water remediation would be needed. One solution would be to install an underfloor secondary containment sump with a flush floor grate to contain the water; however, this would likely add significant cost and may not be feasible.

Standard Z358.1 requires the emergency shower be activated weekly. The designer may want to recommend the owner purchase a portable test rig, which includes a “shower sock” to direct the water to a drum or barrel.

Emergency Natural Gas Shutoff

Many school laboratories have natural gas piped to use points on lab benches or workstations. This presents a potential safety hazard should a student leave a gas valve open or a fire occur. For labs with two or more fuel gas outlets, the International Fuel Gas Code (IFGC) requires a single, dedicated shutoff valve through which all such gas outlets shall be supplied. This allows quick shutoff of all fuel gas to the laboratory from a single location. The valve must be readily accessible, located in the laboratory adjacent to the egress door and must have signage stating, “Gas Shutoff.” Several manufacturers make products specifically for this purpose.

Conclusion

Teaching laboratories provide essential hands-on learning for science students. However, because of potential hazards associated with these activities, designers must understand how to implement engineering controls that minimize exposure risk. This requires understanding proper ventilation procedures, primary and secondary containment strategies and having a solid understanding of the types of learning activities to take place in the labs. Additionally, designers should review all applicable codes and standards and consult the local fire marshal to ensure they are meeting the requirements laid out for each specific type of system.

References

1. Kolesnikov, A, R. Ryan, D.B. Walters. 2001. “Use of Computational Fluid Dynamics to Optimize Airflow and Energy Conservation in Laboratory Hoods and Vented Enclosures.” EPA Labs for the 21st Century Conference.
2. Memarzadeh, F. 1996. “Methodology for Optimization of Laboratory Hood Containment, Volumes I and II.” National Institutes of Health.
3. OSHA. “Code of Federal Regulations 1910.151.” Occupational Safety and Health Administration.