3-3 Professional advice

 
Even after starting the fume hood and no apparent exhaust sound or air movement can be noticed, the following possibilities can be suspected.
 
Is the exhaust fan drive belt broken or cut? 

• If the drive belt connecting the exhaust fan to the motor breaks, this is the first thing to be checked, as it cannot be detected by the electrical system protection circuit (overcurrent or leakage). 

Are there any factors that caused a sudden rise in pressure loss in the exhaust system?

• Inspect the exhaust port for clogging of paper or tissue wipes, and also scrubber or deodorizer for dust or scale, etc.

 
In addition, exhaust sound and exhaust air volume are not necessarily proportional. Please note that the volume of the exhaust air differs depending on the equipment.
 

3-2 Adivice for
Initial support/correspondence 

 
Consult with the lab manager or the facility administrator, and if it is a fume hood that has not been subjected to regular voluntary inspections, immediately carry out an inspection or request it.
 
If a regular self inspection is being conducted, check where the defect is in the local exhaust system based on the report documents.