Three Points on Airflow in Labs

When setting-up HVAC for lab spaces there's often questions on proper airflow and pressure differentials. There's three key points to keep in mind for this:

• Labs should have NEGATIVE air pressure to non lab areas, to prevent any contaminants escaping.
• TC Rooms, Clean room, etc should have POSITIVE pressure to surrounding LAB areas, to keep them free of external contaminants.
• Air in the lab should be completely exchanged every ~10-15 minutes. This ventaliation is critical for negatating spills of volatile compounds.

It's worth noting that for the third point about air exchange, while on paper you'll have the full exchange every ten minutes or so; in practice it will take much longer due to the dynamic nature of airflow. This is why it's best to optomize for the quickest exchange possible. Some labs I've worked in have been as short as 7 minutes, and it still took over 30 to clear out a BME spill.