Achieving Safety and Comfort In Lab Ventilation Design

Aimée Smith, RWDI

In the world of lab design, there are many factors that go into the design of the ventilation system with the priorities being first safety and then comfort. In the past, the HVAC design used high air change rates as a means to provide safety. However, this was a false sense of security as the high air change rate really meant that a lot of air was delivered to the room it did not guarantee control of contaminant concentrations in the occupied space.

A newer approach involves using a lower air change rate until a threshold contaminant concentration is detected within the room or exhaust duct. This then triggers one of multiple options ranging from increased HVAC flows to evacuation of the space. This approach assumes that the sensor location is indicative and appropriate for detection of the contaminant.

This presentation will show how comfort and safety need not be compromised as a result of lower airflow rates. Through the use of good air distribution and siting of exhausts a lower air flow rate can provide the same level of protection as those older high ACH while also providing a comfortable working space. Through this analysis using CFD, the siting of room air monitors will be discussed and shown to be crucial as a component of design for systems that rely on detection.

Learning Objectives

  • Understand how ACH and air distribution affect the performance of the ventilation system;
  • How the ventilation system affects occupant comfort and how comfort can be improved while maintaining a safe environment;
  • The role sensor sitting plays on the performance of the ventilation system; and
  • How CFD can be used in the design process.


Aimée is a Principal of RWDI, and the firm leader for the higher education, laboratory and health care sectors. Aimée is widely recognized among the design community for her deep knowledge of exhaust dispersion and air intake systems and her strong technical understanding of health & well-being of occupants, building energy use, and local microclimate factors including air quality, ventilation, acoustics and wind behavior. Aimee is a licensed Prof. engineer (Ontario), an I2SL and SLCan member.


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