Which device is used to prevent negative pressure in the building by supplying air?

Which device is used to prevent negative pressure in the building by supplying air?

• A. Make up air unit
• B. Backdraft damper
• C. Pressure relief valve
• D. Vent fan

Answer: (A)

Maintaining a balanced building pressure means replacing the air you exhaust with fresh air from outside. A make-up air unit is designed for this purpose: it supplies outdoor air into the space to offset what’s removed by exhausts and ventilation. By continuously introducing outside air, it helps keep the indoor pressure neutral or slightly positive, which prevents doors from being hard to open, reduces unwanted drafts, and avoids backdrafting of appliances. In practice, the make-up air unit often conditions or filters the incoming air and may be integrated with the HVAC system to match the exhaust load. Other options don’t do this balancing job: a damper blocks reverse flow but doesn’t actively provide fresh air; a pressure relief valve releases excess pressure but isn’t a source of supply; a vent fan mainly exhausts air and can create negative pressure if not paired with a supply. So the device that prevents negative pressure by supplying air is the make-up air unit.

Maintaining a balanced building pressure means replacing the air you exhaust with fresh air from outside. A make-up air unit is designed for this purpose: it supplies outdoor air into the space to offset what’s removed by exhausts and ventilation. By continuously introducing outside air, it helps keep the indoor pressure neutral or slightly positive, which prevents doors from being hard to open, reduces unwanted drafts, and avoids backdrafting of appliances.

In practice, the make-up air unit often conditions or filters the incoming air and may be integrated with the HVAC system to match the exhaust load. Other options don’t do this balancing job: a damper blocks reverse flow but doesn’t actively provide fresh air; a pressure relief valve releases excess pressure but isn’t a source of supply; a vent fan mainly exhausts air and can create negative pressure if not paired with a supply.

So the device that prevents negative pressure by supplying air is the make-up air unit.