OSH Answers Fact Sheets
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What are some general troubleshooting tips?
Most of ventilation system problems can be avoided by periodic maintenance and checked by taking measurements of air speed or pressure in the system. Airflow at the hood can be visually checked with inexpensive smoke generators (smoke tubes) or measured with air velometers. Ventilation specialists may be needed to fix or redesign more complicated ventilation problems.
The following simple checklist can be used to evaluate the functioning of ventilation system without extensive measurements or expert help.
Is the fan belt broken or slipping?
Is the fan wired backwards (reversed polarity)?
Is duct clogged with dust?
Is there holes, cracks or openings in the ducts?
Is the air cleaner clogged?
Are any dampers in the duct closed?
Is there insufficient makeup air?
Have ducts been changed to include more length, more or sharper bends, or abrupt diameter changes?
Have additional hoods and ducts been added? (Without proper airflow balancing, some hoods in a multiple system may have inadequate flow or the fan may be too small to handle the additional resistance.)
Has the contaminant source been moved further away from the hood opening?
Is the canopy hood located as close to the source as possible without letting the employees work over the source?
Is an access to enclosing hoods provided?
Is more contaminant being generated at the source?
Are cooling fans causing cross drafts?
Have employees modified the hood because it interferes with their job tasks?
What are some troubleshooting tips for hoods, ducts, air-cleaning devices & fans?
|Low Capture Velocity|| |
|Reduced Face Velocity|| |
|Constant Plugging|| |
|Air Cleaning devices|
|Frequent clogging|| |
|Visible dust in baghouse |
on the clean air side or
in exhaust stack
|Sudden increase in |
|Dirty re-circulated air|| |
|Visible mould or slime|| |
|Insufficient air flow|| |
|Excessive air flow|| |
|Fan does not operate|| |
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