Typically there are many factors involved in maintaining acceptable indoor air quality. This bulletin contains tips and steps that can be taken by non-technical people to evaluate, adjust, and recognize some of these factors. Some systems cycle on and off either due to a computer driven duty cycle or by electrical clock settings for occupied and un-occupied hours.
Power failures can throw off the settings.
Its movement will show when air is being supplied. Air movement should be continuous throughout the workday. A sheet of paper will cling to an intake vent that is at least partially functioning. It is not uncommon to find the dampers closed for reasons of economy and energy management or automatically by a fault control system. Note whether there are any contaminant sources such as rotting material, bird droppings, etc.