Exhaust Fan Negative Pressure

Divide your answer by the system airflow in cubic feet per minute.

Exhaust fan negative pressure.

Both approaches have their advantages. Exhaust fans or smoke ejection fans use negative pressure to remove smoke from a structure during firefighting efforts. Ventry fans are designed for positive pressure ventilation ppv and attack ppa. Negative air pressure should create a slightly cooler environment at least in theory as the fans are working harder to expel hot air.

It the fan moves 200 cfm then 1 970 200 9 85. The article will analyze negative pressure ventilation systems in maintaining air quality house temperature and air movement. Ventry fans are not exhaust fans. The exhaust fan drawing below illustrates how static pressures are measured in ductwork with a manometer.

Positive pressure is simply more effective than negative pressure for aggressive coordinated attack. Negative pressure isolation rooms. This is the exhaust fan s static pressure. Most homes have at least one negative pressure room.

Warm air in your building rises to the upper floors and can result in negative air pressure in the. When a bathroom door is closed if the bathroom has a quality working fan unpleasant odors as well as moisture and humidity are vented out through the fan because the forced air ventilation creates a negative pressure room. With two intake fans and three exhaust fans this setup creates negative air pressure. My house currently has a blower door test result of 5 200 cubic feet per minute at 50 pascals of pressure difference 5 200 cfm50.

When should negative pressure ventilation be used. The negative pressure created by the exhaust fans is really something we have to worry about. The more airtight the house the bigger that negative pressure will be. Let s put some numbers to that idea.

Like combustion appliances exhaust fans can remove too much air and cause negative air pressure. When retrofitting a standard patient room for use as a negative pressure isolation room it is not often practical to exhaust the air directly outdoors as required. Static pressure in fan systems is typically less than 2 sp or 0 072 psi. A pressure differential between the duct and the atmosphere will cause the water level in the manometer legs to rest at different levels.

Conversely if the smoke was localized then we would place the fan about 6 from the door on the inside of the house facing out thus creating a negative pressure in the house.