Optimal Indoor Air Quality inside Buildings

Indoor Air Quality (IAQ) refers to the air inside a structure that affects the health and well-being of occupants, it should not contain more than acceptable levels of contaminants determined by governing authority’s code/bylaws and a majority of the people exposed to this environment shouldn’t express dissatisfaction. Creating and maintaining a proper environment for user comfort is the primary function of a building, depriving the user of it defies the purpose and shouldn’t be taken lightly.

SBS (sick building syndrome)

In case, proper air quality is not maintained, a feeling of illness might persist among a majority of occupants of a conditioned space, commonly termed as the Sick Building Syndrome. Symptoms of this syndrome include headache, fatigue, irritation in eyes, nose & throat, shortness of breath, etc., and are likely to stop once the occupant exits the building. Let’s understand the reasons behind poor air quality and SBS:

  • Inadequate ventilation- insufficient supply of outside air, poor mixing & circulation, fluctuations in temperature & humidity (High CO2 because of poor ventilation larger than 1000 ppm)
  • Air filtration problem- lack of maintenance of HVAC systems.
  • Rate of emission from sources indoors- generation of combustion gases indoors by heating, Environmental tobacco smoke (ETS), etc.
  • Age of indoor structure- aging and degradation of a structure release harmful compounds in the environment.
  • Harmful materials and Volatile organic compounds - use of the chemical substance for building materials like formaldehyde from adhesives, such adhesives are present in floor, walls, furniture, and ceiling of structures.

Ventilation compliance   

Well ventilated spaces efficiently circulate the air inside and replace it with fresh air and hence the contaminants can be flushed out of the interior space periodically. Naturally ventilated spaces must be eternally open to the outdoors and within 25 feet of operable wall or roof openings. At least 4% of the net occupiable floor area must be taken up by ventilating devices. If an opening is covered with louvers or else partially obstructed, an unobstructed area should be considered for calculations. In case of indirect ventilation outdoors through an adjacent room, the opening between the rooms must be permanently unobstructed and be at least 8% of the area of the interior room. Occupants must have a readily accessible way to control and operate the openings as per their comfort. For acceptable benchmarks and metrics refer The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) standard.

HVAC Protection

The heating, ventilation, and air conditioning system permanently installed should be avoided. If permanently fixed air handlers are used during construction, filtration media (minimum efficiency of 30%) must be used at each return air grille. All filtration media should be replaced immediately before the occupancy. Equipment needs to be carefully cleaned and stored in a dry location; ducts and equipment openings can be sealed with plastic for protection.

Image Credits: National Air Filtration Association

Environmental Tobacco Smoke (ETS) Control

To begin with, smoking should be prohibited in the building whereas on-property smoking within 25 feet of entries and outdoor air intakes can be allowed. Smoking areas should also be located away from crowds of building occupants or pedestrian traffic to avoid passive intake. If a smoking room is planned inside the building, care should be taken such that separate ventilation systems are installed, tested for efficiency, and isolated from the non-smoking portions of the building (contain, capture, and remove). Smoking rooms must directly exhaust air to the outdoors, away from air intakes and building entry paths, hence, no recirculation of ETS-containing air happens. Designated signages that mark the zone as smoking/non-smoking should be indicated throughout the property.

Specifying less harmful materials

As they say, prevention is better than cure, a practical way to prevent indoor environmental quality problems is to specify materials that release fewer and less harmful chemical compounds. This technique is generally much more effective and less expensive than identifying and solving the problems after they occur. Chemically driven materials like glues, tints, carpets, adhesives, composite wood products, and furniture with low levels of irksome off-gassing can reduce occupants’ exposure to diseases. Appropriate arrangement of delivery and sequencing of building activities can also help in reducing material revelation to moisture and absorption of contaminants.

Allowing occupants to control their environment

One step further would be realizing that different occupants have different thermal comfort levels. Working with them to assess their needs, providing individual illumination controls and area thermostats can advance inhabitants’ comfort, efficiency and save energy. Personal thermostats are an enabler for them to meet their seasonal heating/cooling needs more precisely, this can be done by underfloor air distribution systems.


A simple way to regulate the air quality without the use of active energy-consuming devices is by introducing greenery indoors and at the site level as well to control the microclimate. Plants help to improve the psychological and physiological environment as they use carbon dioxide for their processes and release oxygen into the environment, refreshing the occupants’ environment and mood as well.

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