To limit the probability that inappropriate installation will interfere with the opening or closing of dampers, which could lead to an inability to balance the flow of intake and exhaust air, which could lead to:

• the inadequate delivery of warm air or the return of cold air, which could lead to an inability to maintain adequate relative humidity or indoor air temperatures,
• inadequate ventilation, which could lead to the inadequate control of:
  • relative humidity, which could lead to condensation, which could lead to the growth of mould and mildew, or
  • airborne pollutants, or
• insufficient combustion air for fuel-burning appliances, which could lead to incomplete combustion.

This is to limit the probability of:

• negative effects on the air quality of indoor spaces, and
• the inadequate thermal comfort of persons.

This is to limit the probability of harm to persons.

To limit the probability that inappropriate installation will interfere with the opening or closing of fire dampers or fire stop flaps, which could lead to an inability to retard the spread of fire and smoke to other parts of buildings, which could lead to harm to persons.

To limit the probability that inappropriate installation will interfere with the opening or closing of fire dampers or fire stop flaps, which could lead to an inability to retard the spread of fire and smoke to other parts of the building, which could lead to damage to the building.