Laboratory Ventilation Design Levels

In modern laboratories, large numbers of hazardous substances may be used.  During reactions, transfers and other handling procedures, hazardous substances may become airborne and this may cause harm to people in the laboratories.   Therefore, laboratories are equipped with Exposure Control Devices (ECDs) such as fume hoods and other exhausted enclosures to ensure all hazardous chemicals and airborne emissions are safely contained or captured.  These ECDs must work together with the building air supply system that also has the task to maintain temperature and humidity requirements of the indoor environment.   Together, this is known as the Laboratory airflow control system(LACS).   Figure 1 is a simplified diagram showing the various components of an LACS.

In principle, the protective capability afforded by a lab ventilation system must be commensurate with the level of risk associated with the airborne chemical hazards that may be generated.  The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) has recently developed a guidance document Classification of Laboratory Ventilation Design Levels 1. The five Lab Ventilation Design Levels, LDVL-0 to LDVL-4, represent systems that offer the lowest to the highest level of protection (Figure 2).  Interestingly, this also corresponds quite well with the Chemical Safety Levels 2 1 to 4 proposed by the American Chemical Society.

Figure 1  Simplified diagram of laboratories and LACS showing critical components and attributes.

Figure 2  Risks associated with airborne hazards and the levels of protection associated with the range of LVDLs.