MD15128 Scope of Work speaks to Canadian fumehood test regulations and Canada and fumehoods.
Note: Fume Hood Certification is to be done on an annual basis.
For existing fume hoods there must be a tracer gas verification every 5 years and if this has not been done it is suggested that a budget be included to do such as soon as possible. It is suggested that these tests can be phased in at 20% of fume hoods for each year over the next five years on an ongoing basis.
The tracer gas tests are to prove sash movement containment tests and for VAV fume hoods VAV response and stability tests. For VAV systems the two tests can be done at the same time.
Preliminary Procedures MD15128 Scope of Work
Where access allows, using a smoke pencil, check the integrity of all seals around light and other fixtures.
Check that the sash stop is still in place and operates properly.
Check that all baffles are in the same positions as in previous tests.
Determine whether significant sized laboratory equipment inside the hood is the same as for previous tests.
Visually inspect the fan and motor, pulleys and belt. Is belt at correct tension? There should be approximately .5 “of play.
Are fan and motor pulleys in good shape? Are they worn or slipping?
Ask the service provider and user if belts and pulleys have been changed since last set of tests.
Inquire as to what the normal sash face working height is. It is usually 300 mm (12”) 450 mm (18”) but can be as much as 600 mm (24”).
MD15128 Scope of Work
Sash Face Velocity Tests
Measure the length of the sash opening. Divide by 10. Using a black magic marker, mark these increments on the bottom or top of the horizontal length of the sash. Mark both sides of the sash face vertical at 6” heights.
Using a thermal anemometer with articulated probe measure the velocity in m/s or fpm in the middle of each of the resultant squares. On a 1500 mm (60”) by 300 mm (12”) sash opening there will be 20 readings.
There should be a minimum of 15 seconds between each reading.
Total the 20 test readings and divide by 20 to determine the average air velocity in m/s or fpm through the sash face opening.
The average velocity reading between of .50 m/s (100 fpm) ( between .45 m/s and .55 m/s) should be achieved. Report findings.
Depending on how the contract stipulates you may have go to the exhaust fan and rectify.
If this work is not stipulated in the certification contract it may be an extra. This rectification is usually not included in the contract as it is not known how many fume hoods have to be adjusted and this would make it very difficult for the contractor to quote.
Provide proof of annual meter calibration for MD15128 Scope of Work.
If between .45 m/s and .55 m/s is achieved do smoke pencil tests.
One should be aware if there are 2 “off-the-scale” readings the fume hood baffles should be adjusted and the tests redone.
Be aware that these “off-the-scale” readings are only indicative of faulty fume hood operation if the fume hood is empty. It must be mentioned that fume hoods are seldom empty when tests are being done as fume hoods are not used in an empty condition. This will affect the number of “off-the-scale” readings.
Smoke Pencil Tests MD15128 Scope of Work
With the sash at the designated working height, 300mm or 450 open, using a smoke pencil test for:
Note whether acceptable or not.
Cross Draft Velocity Tests MD15128 Scope of Work
Using a thermal anemometer positioned .5 m (18”) ensure that there is not a draft across the sash face opening exceeding 50% of the average face velocity. The average face velocity ideally being .50 m/s or 100 fpm.
Smoke Containment or Visualization Tests MD15128 Scope of Work
Place a smoke emitter in the centre of the fumehood, energize and observe to ensure proper containment, which means all smoke must be carried to the back of the hood.
Ensure that the smoke emitter does not produce more smoke than the fume hood rate of exhaust. If not, smoke will migrate to the front of the fume hood and produce a false “fail” test.
For example if a 40” wide by 18” sash open is in use, this is a cross sectional area of 5.0 sq ft. If there is an average air velocity through the sash opening of 100 fpm, the fume hood can exhaust 500 cfm of smoke. If the smoke emitter produces more than 500 cfm of smoke, the excess will migrate to the front of the fume hood.
After the smoke emitter is turned off, the smoke should be cleared from the fume hood in 60 seconds or less.
Some departments have been known to use “theatrical” smoke devices to do their own tests. This is wrong as these devices cannot be set to produce controlled volumes of smoke.
Monitor and Alarm MD15128 Scope of Work
When the average sash face velocity is determined, check that the fume hood monitor is indicating the same velocity reading.
Calibrate the monitor as required.
Lower or raise the sash to cause the sash face velocity to change and note whether the audible alarm sounds.
Calibrate the alarm as required.
Fume hood labelling
Attach a certification label to the fume hood which indicates:
Test company. Technician. Signature. Date. Average sash face velocity. Sash face open position.
Fume hood log books
Provide a 1” white 3 ring binder log book for each fume hood. Leave at the fume hood. Include above test result sheets in this log book.
The cover page should include:
Fume hood Master Document
Provide 2 suitably sized white 3 ring binders to the contracting authority. Contained in these binders will be a copy of the test sheets for all the fume hoods tested.
The cover page should include:
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