How do you know when a fume hood is not performing the way it should? The short answer is a fume hood flow alarm. Unlike biosafety cabinets, fume hoods aren't legally required to come with an airflow sensor, which is why many manufacturers don't include them on new units.
Factory Installed Alarms
In the instances when alarms are included in new units, we have found that there is much to be improved on. Many claim to be factory calibrated but that does not mean they will be accurate in your lab's unique conditions. Cross drafts, exhaust fans, duct run and a number of other factors make your lab unique.
What To Look For In Airflow Alarms
Inline duct sensors that measure airflow in the ductwork
Digital readings for more information than analog monitors
Temperature and pressure readings for a more robust system
Color alarms recommended by NFPA in addition to audible alarms
Alarm notification via text or email
VAV vs CAV Considerations
If you are using a CAV system then the airflow monitors provided by the manufacturer can be used. If you are using a VAV system then the monitors from the manufacturer will not work and will need monitors compatible with the VAV system.
Two Airflow Standards To Know
NFPA 45-2015, Section 7.8.7: A measuring device for indicating that the hood airflow remains within safe design limits shall be provided on each chemical fume hood.
ANSI Z9.5-2012, Section 8.10: All Hoods and exposure control devices shall be equipped with a flow indicator, flow alarm, or face velocity alarm indicator.