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 bio safety cabinets, fume hoods aren't legally required to come with airflow sensor. Which is why many fume hoods 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 labs unique conditions. Cross drafts, exhaust fans, duct run and number of other factors make your lab unique. This means the fume hood flow alarm will need to be recalibration after installation.
Couple that with the fact that many of these alarms are sidewall mounted, non-customizable and don't have inline duct sensors.
What To Look For In Airflow Alarms
There are a number of different styles of airflow alarms out there, so finding the right one isn't always easy. We have installed countless alarms and here are the key things we look for:
- Inline duct sensors: This measures the airflow in the ductwork to the fume hood. These sensors can monitor overhead ventilation or disruptive airflow in front of the sash.
- Digital readings: This give you more information than an analog monitor and can help you catch issues before they arise.
- Temperature and pressure readings: some sensors allow you to capture this along with airflow reading, leading to a more robust system.
- Color alarms: color alarms are recommended by NFPA in addition to audible alarms. Where a green light means you okay to operate in the unit and a red light means you are not.
- Alarm notification: Alarm systems now come with capabilities to alert you via text or email. This can help notify the right person as soon as something goes wrong.
Additional Fume Hood Flow Alarm Considerations
Variable Air Volume (VAV) vs Constant Air Volume (CAV)
The type of system you are installing your fume hood into makes a big difference in the alarm controls to use. If you are using a CAV system then the airflow monitors provided by the manufacturer can be used. (we however recommend using a third party airflow monitor even when installing into CAV systems for accuracy) If you are using a VAV system then the monitors from the manufacturer will not work. They will instead need monitors that are 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... The measuring device for hood airflow shall be a permanently installed device. It shall provide continuous indication to the hood user of adequate airflow and alert inadequate hood airflow by a combination of an audible and visual alarm."
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 as applicable to alert users to improper exhaust flow.”
Fume hoods and other air containment systems are the front line of defense against toxic fumes in labs across the US. These systems help protect lab personnel and research products alike. We can help install the correct fume hood flow alarm for your unique lab. Give us a call at (712)-309-3680 or contact us online.