Proper airflow is vital to personnel who are working with corrosive, hazardous, or volatile materials in a cleanroom. Safety hinges on proper fume hood exhaust monitoring; it alerts workers when the airflow drops below calibrated levels. In Part 1, we discussed some available options in fume hoods. With a fume hood selected, you can focus on maintenance, replacing equipment, and selecting the monitoring system.
Regular maintenance will likely be an annual or semiannual certification consisting of a velocity test with a thermal anemometer at predetermined points. The points depend on the size of the sash opening. The certification also includes calibrating the alarm and performing a smoke visualization test to prove airflow direction and smoke containment. In addition to certification, facility personnel should carry out scheduled checks on the blower motor belt.
Your fume hood monitor does not need to be replaced until the system doesn’t function any longer or it doesn’t calibrate properly.
Selecting the Monitoring System
The monitoring system is obviously a critical part of the fume hood as it is what will tell you when levels are dangerous. Your choice will ultimately depend on how much data you want to receive. Some systems will set off an audible and visual alarm when velocity drops a set percentage; others will actually give a read out of the velocity. Your customer may require the read out for documentation. There are monitors that don’t give both alarms, but your safest bet is to go with one that has both the audible and visual alarms.
Remember that when installing your fume hood, you need to look at the layout of your lab. You don’t want supply vents or filters directly in front of the hood. It’s best to have a full ASHRAE 110 test at the initial certification. Additionally, it is best to have your fume hoods on dedicated exhaust systems. If one unit needs an adjustment, it usually requires a rebalance of any other hoods within a shared system.
For cleanroom certification and validation, contact the experts at Gerbig Engineering Company: 888-628-0056 or firstname.lastname@example.org.