Variable Air fumehood tests speaks to how to do variable air fumehood tests that are required to be done on an annual and five year period as dictated by Department of Public Works MD15128 guidelines in Canada in government departments in Canada.
Non government laboratories in Canada and all laboratories in the USA and elsewhere in the world are required to be done on an annual and five year period as dictated by ASHRAE 110 guidelines.
The variable air volume fume hood tests required are as explained below:
Sash velocity tests at various openings. Cross draft stratification tests at various openings. Minimum flow test. Smoke visualization tests at various openings. Smoke containment tests at various openings. VAV response and stability.
Five year interval:
Tracer gas test – static sash positions. Tracer gas test – effect of sash movement. Fume hood alarms.
Sash velocity test
Measure the sash opening air velocity at multi points in the sash face opening. The average desired for general fume hoods is 100 fpm, plus or minus 10%. The average desired for perchloric fume hoods is 120 fpm, plus or minus 10%.
Cross draft stratification test
Measure the cross draft velocity from all directions across the sash face opening for the fume hood. It should not exceed 50% of sash velocity test.
Minimum flow test
Test to ensure fume hood minimum flow requirements are met.
Smoke visualization test
Using a hand held smoke emitter test for blow back of smoke from the fume hood.
Smoke containment test
Using a bulk smoke emitter test for smoke exhaust and smoke total clearance from the fume hood.
Flow response test
Raise and lower the sash 3 times during a 5 minute period. The sash is in the closed position for 30 seconds then to the working height for 60 seconds during 3 cycles. Return to stable control within 3 seconds as proven by sash opening velocity tests. This test and the Sash movement containment test can be done simultaneously.
Flow stability test
The sash is closed for 5 minutes and opened for 5 minutes and then check for stable control flow. It is measured with a velocity probe place at the lower baffle vent opening. This test checks the ability to control at minimum and maximum sash open position.
Tracer gas test
A mannequin with a sensor positioned at its nose is used. The test gas emitter is moved left, right and center as is the mannequin. Gas used for FH tracer gas tests is Sulphur Hexafluoride (HF6).
Sash movement containment test
The sash is closed for 30 seconds and opened for 60 seconds through 3 cycles and gas tracer tests are done.
Completion VAV Fume Hood Tests