Laboratory Ventilation Basics
Laboratories can be dangerous places.
Because laboratories handle toxic chemicals, combustible substances, flammable solvents, harmful organisms, obnoxious vapours and so on…
Various control measures are necessary to make laboratories safe and comfortable places to work.
Most people are aware that only highly trained and authorised personnel are allowed to work in laboratories, and they use PPE (Personal Protection Equipment such as lab coats, safety goggles, respiratory masks etc). However, some may not know that a lot of effort goes in to incorporating appropriate engineering controls while designing and fitting out new laboratories. This provides safety at three levels – laboratory users, wider organisation and the surrounding neighbourhood.
For lab designers, understanding of the type of research/activities carried out and regulatory compliance sought by clients is an important step to determine the type and level of ventilation needed for their new facility.
Ventilation is important from a safety as well as financial point of view as it demands major capital and operating costs. Laboratories are energy intensive environments, consuming 4–6 six times more energy per square metre than standard office or commercial buildings and more than 60% of a laboratory’s energy consumption can be attributed to the HVAC system (Manufacturing Chemist).
Laboratory ventilation is a complex topic needing specialist input. However, in this article we present an overview and some basics.
HVAC & Lab Ventilation:
A more commonly used term HVAC - Heating, Ventilation, and Air Conditioning - is the technology of indoor and vehicular environmental comfort. Its goal is to provide thermal comfort and an acceptable indoor air quality. Laboratory ventilation, a part of the HVAC system, is the supply of a fresh/clean air to displace contaminated air and dilute it to safe levels. It consists of two vital factors - air handling and filtration systems.
A basic HVAC unit can be as shown below,
Air is continuously exchanged between buildings and their surroundings. The rate at which air is exchanged is an important property for the purposes of ventilation design and heat loss calculations and is expressed in ‘air changes per hour’ (ach).
Air changes per hour, or air change rate, abbreviated ACH OR ACPH, is a measure of the air volume added to or removed from a space (normally a room or house) divided by the volume of the space. If the air in the space is either uniform or perfectly mixed, air changes per hour is a measure of how many times the air within a defined space is replaced.
Different laboratory areas and rooms in the building will need a different number of air changes. Rooms containing fume cupboards and higher containment need a greater number of air changes than a general laboratory.
The type of material handled in the space will determine if the exhaust needs treating (e.g. HEPA (High Efficiency Particulate Absorption) filters, scrubbers) before discharging into the atmosphere or re-circulating back. For example, biology laboratories, BSL (Biosafety Level) 1 to 4, will involve increasing hazard level and filtration needs. BSL1 being the simplest and BSL4 the most complex.
Pharmaceutical clean room environments need a very high number of air changes as well as HEPA filtration for supply and exhaust air. Check our guidance on clean rooms here.
Guidance on ACH:
In the UK, there are no prescriptive values for air change rates. The rate determined depends on the type of room and the activity being undertaken. Typical industrial applications range between 5 and 15 air changes per hour (CIBSE).
A word of caution about the ACH rate - Ventilation is a tool for controlling exposure. Since a ventilation system designer cannot know all possible laboratory operations, chemicals to be used, and their potential for release of fumes and other toxic agents, single air exchange rate cannot be specified that will meet all conditions.
Furthermore, air changes per hour is not the appropriate concept for designing contaminant control systems. Excessive airflow with no demonstrable safety benefit other than meeting an arbitrary air change rate can waste considerable energy.
An early and accurate assessment of clients’ needs, and risk levels through a collaborative approach between lab users, designers, health & safety representatives and M&E engineers/consultants to propose an appropriate ventilation strategy is recommended.
Some or all the criteria below can be used in determining what that looks like:
- Facility Layout and workflow
- Temperature, relative humidity
- Air pressure differentials between rooms
- Number of air-changes for each room
- Air velocity and airflow pattern
- Number of particles in the air
- Filters (type, position)
To minimise the energy consumption and environmental impact of ventilation equipment, numerous initiatives have been put in place by the industry to make future labs smarter. New ways make ventilation central to the design process involving M&E and key stakeholders early in the process, considers it as a dynamic than static process making monitoring and quality control central and the design process focuses on space as activity based zoning and risk assessment for improved efficiency and better control.
While choosing a new building for laboratory use, it is important to assess the size of the plant room needed and whether enough space is available for distribution of services. Thought needs to be given to structural slab to slab height and to creating sufficient space for a network of supply and exhaust ducts in the chosen building.
Recently, we worked on a project located on an upper floor of a busy city centre building. Initially, the client had requested high ACH rates throughout the lab (BSL2) area. But constraints with the external and roof top plant space, the lack of ceiling space for extensive ducting and the landlord’s reluctance to grant permission allowed us to re-visit their ventilation needs. After individual room analysis and risk assessment a new flexible ventilation strategy was proposed requiring a lesser plant area and improved future energy consumption.