ASHRAE defines acceptable indoor air quality as air in which there are no known contaminants at harmful concentrations as determined by cognizant authorities and with which 80% or more people exposed do not express dissatisfaction. Indoor air quality in commercial office buildings is important because it can affect occupant comfort, health, and work productivity. Scientific studies have confirmed a direct correlation between poor indoor air quality and increased employee sick days and workers compensation claims. Therefore, improving indoor air quality in commercial office buildings is a benefit to both business employees and owners.
There are a variety of factors that can contribute to poor indoor air quality in the workplace. This article addresses certain parameters of indoor air such as temperature, relative humidity, carbon dioxide concentrations, carbon monoxide concentrations, volatile organic compound (VOC) concentrations and small particle concentrations; however, it is important to note that there are other factors that can negatively affect indoor air quality.
Thermal conditions (temperature and relative humidity) should be maintained within recommended ranges found in ASHRAE 55.2004 to maximize occupant comfort levels. Additionally, controlling relative humidity within the space can also prevent mold growth from occurring. The presence of mold growth within an indoor environment can cause occupants to experience allergy type symptoms. Elevated indoor carbon dioxide concentrations from under-ventilated office areas can cause occupants to feel fatigued. Elevated indoor carbon monoxide concentrations from combustion equipment or nearby parking garages can present a hazardous condition for building occupants being that carbon monoxide is a highly toxic gas which is lethal when exposed to elevated concentrations.
Volatile organic compounds (VOCs) from office furniture, flooring, paints, printers, copiers, cleaning products and deodorizers can cause adverse reactions in certain occupants. Typical symptoms of elevated indoor VOC concentrations have been described as coughing, sneezing, allergy type symptoms, and burning or itching eyes.
Excessive small indoor particle concentrations (particles that are small enough to enter the respiratory system) can be a result of insufficient cleaning activities, excessive paper shredding or construction activities and can cause building occupants to experience symptoms similar to those experienced by elevated VOC concentrations.
So what can be done to improve indoor air quality? Best practice would be to implement monitoring equipment that continually measures the indoor air quality parameters mentioned above. Continuous measurement of the indoor air would enable a building manager to not only confirm that the indoor air quality is within industry acceptable levels, but also detect any changes in the indoor air quality so that corrective measures could be performed prior to receiving occupant complaints.
Another good practice is to install high efficiency filtration (within the static capability of the HVAC systems) throughout the building. A filter maintenance schedule should also be developed to prevent the use of dirty filters. Routine cleaning procedures should be performed throughout the building. Appropriate ventilation rates should be ensured to effectively dilute indoor contaminants and to reduce carbon dioxide concentrations within the building. The selection of certain building materials and components such as low-emitting VOC paints, flooring, furniture, and low-emitting copiers and printers will limit the amount of contaminants introduced into the indoor environment.
Maintaining good indoor air quality is an ongoing effort that requires an understanding of factors that can negatively impact indoor air and the appropriate preventative measures that should be implemented.