HVAC Ventilation System | HVAC Exhaust Air System

HVAC Ventilation System

  • Outside air intake shall be sufficient to allow building spaces to meet the definition of acceptable indoor air quality and minimum ventilation rates defined in ASHRAE Standard 62.1 version for ventilation for acceptable indoor air quality for commercial buildings including industrial buildings and 62.2 for residential buildings.
  • Ventilation calculation shall be based on ventilation rate procedure method mentioned in the ASHRAE Standard 62.
  • Buildings/Facilities as an overall shall be maintained at a positive pressure with respect to atmospheric pressure.
  • Outside air intake shall be sufficient to maintain a space/room pressure as defined in Table II for inside the building, with doors and windows closed.
  • Ventilation rates shall be provided at a minimum of 10 L/s (21 CFM) of outside air intake per person or 5 Liter per second per square meter of floor area for areas/space not specified in ASHRAE 62 the greater value shall be selected.
  • Outside air intakes shall not be located where air contaminants are brought in from, for example, lab hood exhausts, vent pipes, vehicles, kitchen exhausts and cooling tower or pooled water emissions. The distance from the air intake to sources of contamination; prevailing wind speed and direction; and objects that might influence air flow should be considered in this evaluation.
  • The elevation of the outside air intake for all HVAC systems shall be minimum 1.5 m above the roof/slab of the building. Where this is not possible, outside air intake from the side of the building may be considered.
  • Battery room ventilation rate shall be calculated based on battery manufacturer recommended rate but it shall not be less than 5.1 liter per second per square meter of floor area of the room.

HVAC Exhaust Air System

  • Exhaust rate for rooms/spaces calculation shall be based on rates mentioned in the ASHRAE Standard 62.1.
  • Air from toilets, locker, kitchen, break and ablution rooms shall be exhausted directly to outside.
  • No air from these areas shall be re-circulated to HVAC system or adjacent rooms.
  • Make-up air shall be provided for all areas provided with exhaust. Make-up air shall be sufficient to prevent the odors transfer to adjacent areas within the building.
  • In no building/facility shall the total exhaust air quantity exceed the total outside air intake quantity. Energy recovery units shall be installed in such cases to recovery energy.
  • Non-general exhaust duct sizing criteria shall conform to ACGIH Industrial Ventilation Manual.
  • The laboratory exhaust systems shall be in accordance with AIHA Z9.5.
  • Exhaust air from kitchen hood shall be exhaust directly to outside.
  • Air in battery room shall exhaust directly to outside (no circulation) based on minimum recommended exhaust rates from battery manufacturer and shall not be less than 0.3 cubic meter / min per square meter (1 cfm/ft2).

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