Engineers who design laboratories in hospitals, R&D facilities, and educational buildings face the challenge of meeting various standards and code requirements for ventilation systems while optimizing energy efficiency.
One source of contention among those who engineer laboratory ventilation systems is the correct value for air changes per hour (ACH). The reason for the debate is that the appropriate ACH value depends upon the type of facility in which that lab is located, the standards used by the facility, and the level of code enforcement by the facility. In fact, the ANSI Z9.5 standard indicates that ACH is not the correct concept to use when designing lab ventilation systems because it is impossible to specify a value for air exchange suitable for all conditions. To add to the complexity of the design process, engineers also need to optimize the energy efficiency of the ventilation system. According to statistics cited in Consulting and Specifying Engineers, ventilation systems account for 44 percent of the energy consumption in labs. What does an engineer need to consider when designing laboratory ventilation systems? How can engineer minimize energy consumption?
Considerations for Engineering Laboratory Ventilation Systems
According to ANSI Z9.5, ACH value does need to be taken into account when designing the dilution ventilation systems used to control the accumulation of chemical fumes and odors. This standard requires the use of variable air volume (VAV) ventilation hoods, which are inherently energy efficient. For further energy savings, engineers should use a diversity factor when engineering the ventilation system along with an airflow alarm to indicate when the system is operating beyond capacity.
Other considerations for designing lab ventilation systems include:
• Expansion factors
• Minimum and maximum ventilation rates
• Number of hoods and users in the lab
• Use patterns
• Sash management
In addition, to minimize risk, engineers need to collaborate closely with the chemical consultant on their projects.