Mechanical Ventilation

Mechanical ventilation is accomplished with the help of heating and air conditioning units with fans, that circulate air through the house, and in some instances, bring in outside air and exhaust air back to the outside. Spot mechanical ventilation is usually a bathroom or kitchen exhaust fan, a ceiling fan, but usually there is no way to bring enough fresh air in to compensate for the exhausted air, but sometimes natural ventilation is used. People install large exhaust fans in their home, thinking it could alleviate moisture or allergy problems, without installing a system to bring in fresh, outdoor air. Without fresh, or outdoor, air induction will cause infiltration of air, through the walls, causing even more humidity and irritants in the home.

When indoor pollutants cannot be controlled at their source, mechanical ventilation should considered.

Local mechanical ventilation types include bathroom exhaust fans, range hood vents, and clothes dryer vents. These try to exhaust indoor pollutants (moisture, smoke, clothing lint, etc.) at their source.

Gas clothes dryers, gas stoves, fireplaces, and other objects will actively burn oxygen, increasing the need for ventilation, and can cause negative pressure in a home, drawing air through walls and floors, and from the soil. Exhaust sources should be used, and some should also receive a source of outside air.

General mechanical ventilation commonly is known as the heating and air conditioning system. Ductwork in the home distributes air throughout the home, diluting indoor pollutants. Home remodeling, cleaning, pesticide use, new furnishings, new or newly dry cleaned clothing, and cooking are common activities that need increased ventilation to reduce indoor pollution.

Many commercial office buildings today have ventilation systems that bring in fresh outdoor air and exhaust stale indoor air back outside. An energy recovery unit, or ventilator, also known as an air exchanger, performs this process in some homes. Often installed close to the heating and air conditioning units, they preserve the desired heat or coolness from the inside air before they are exhausted outside. While they increase energy costs, they also reduce indoor pollutants and moisture. One air filter that can help with the issue of indoor air pollutants is called the Oreck Air Purifier.