Indoor Air Quality and Ventilation: Overview
It is easy to overlook the role of ventilation in the indoor environment. For every type of building, it is necessary to provide some degree of ventilation (air supply and return/exhaust) to building occupants. Lack of ventilation in an occupied, indoor environment quickly leads to issues of comfort (temperature, humidity, air movement). In hazardous locations (e.g. laboratories and chemical storage rooms), lack of ventilation could lead to health- and fire hazards.
Before the widespread use of electrical power, buildings and homes used natural ventilation, which made clever use of the natural properties of air with changes in temperature, and air movement patterns at the specific location/site of a building. Floor plans, room layout, placement of windows, doors, fireplaces, ventilating structures, etc. took advantage of these properties to direct air currents throughout a building.
Since electricity came into popular use, ventilation is accomplished mechanically. Fresh, outside air (OA) is mechanically brought into a building by an Air Handling Unit (AHU). As the air enters the AHU, it is filtered (typical MERV rating at Lehman College 8-13) to remove particles (e.g. dirt, dust, mold spores) which would, over time, damage air handling equipment and contaminate indoor spaces. Depending on the season, air is tempered (heated or cooled) and then distributed throughout the indoor environment, conveyed through ductwork.
Indoor air destined to be recirculated is carried back to the AHU via the return/exhaust ductwork. For indoor spaces containing no hazardous materials, some of the air is recirculated back into the system (filtered once again). Building codes require that ventilation systems be designed so that fresh OA comprises about 33% of indoor air in non-hazardous locations (e.g. offices and classrooms). During times of the year in which OA does not need to be heated or cooled, air inside a building can be 100% OA.
After the energy crises in the US of the 1970s, architects and engineers began designing new buildings that were nearly airtight, never allowing any air to stray in or out through windows, doors, and other openings. The worthwhile goal of conserving energy, gave rise to Building-Related Illness (“Sick Building Syndrome”); one notable case being the headquarters of the Environmental Protection Agency.
Ventilation systems are designed at the same time as other building systems (plumbing, electrical, mechanical, etc.) and are difficult to change once they have been built. During the design phase of a new building, ventilation systems take into account the proposed use of the building/interior space, with some consideration for future modifications. Renovations must take into account new/modified ventilation needs, especially in cases where existing spaces are re-purposed for vastly different occupancies, or for use as hazardous locations (laboratories, chemical storage rooms). For this reason, multiple NYC agencies (Department of Buildings, FDNY) are involved in the approval/permitting process for hazardous locations.
Inadequate ventilation, even in non-hazardous locations, can result in non-specific respiratory symptoms, headache, fatigue, etc. that begin soon after entering a building, and abate upon leaving the building. If you and others in the same space begin to notice these symptoms, please contact the Office of Environmental Health & Safety (x8988, x8978) to request an Indoor Air Quality (IAQ) evaluation. Although the indoor environment is unlikely to become hazardous in the absence of hazardous materials, an IAQ evaluation will determine where the problem lies so that it can be quickly corrected.
Indoor Air Quality Links
- OSHA Indoor Air Quality
- EPA Indoor Air Quality
- NIOSH Workplace Safety & Health Topics: Indoor Environmental Quality
Last modified: May 21, 2014