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We mentioned in a previous article that all ventilation systems requires inspection and testing. Training on routine and emergency operating procedures should also be provided and all three these elements should be incorporated into a good ventilation control program.

Let's discuss these points separately:


Never assume the system is operating properly just because the fan is running.

Some things to be considered during inspections are:

  • Determining the velocities at which the system is to operate

  • Doing visual checks of the system – physical condition of ducts, dampers, hoods, stack, motor, fan, blades, belts

  • Checking the electrical system regularly

  • Checking noise levels from fans (increase in noise levels is an indication of problems; any increase in noise could also raise noise exposure levels to above legal limits)

Difficulty in opening doors in buildings with local exhaust may indicate that not enough make-up air is being supplied, so that the efficiency of the system is reduced. The frequency of inspections depends on the manufacturer’s recommendations, how often the system is used, and the form and concentration of the contaminant(s) being removed.


The following are some important aspects of testing:

  • Static pressure in system – unless test locations have been provided, caution must be used in drilling holes in duct work. The inner surface of the duct must remain smooth or the instrument may give a false reading

  • Air current test (i.e., smoke tube tests) are not an absolute indicator of hood efficiency

  • Testing should be done under the worst conditions (i.e., at peak operating times)

Determine the correct direction of rotation of the fan blades. Once this is determined, indicate the direction on the fan case. This will help in future inspections/maintenance.


Training requirements should include the following:

  • Familiarity with the Occupational Health and Safety Act and Regulations

  • The role of ventilation in contaminant control

  • Breakdowns which cause hazardous or nuisance conditions

  • How to handle fire in ducts

  • Knowledge of tests carried out (to reinforce why there is such a ventilation system)

  • Position required to be in while working near exhaust hood

  • Shutdown procedures of fans, etc.

Ventilation Control is a critical part of your Health and Safety. Curvent International has been assisting companies with their control programs in all of these areas. Make sure that you use experts when determining if you have the right control program in your company.

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