“Stale air” refers to indoor air that lacks proper exchange with fresh outdoor air due to inadequate ventilation. This environment can make you sick, not because of the air itself, but due to the elevated concentration of pollutants trapped within. Modern, tightly sealed buildings designed for energy efficiency can inadvertently concentrate these airborne agents. This poor air quality allows contaminants generated indoors to accumulate rapidly, increasing exposure for occupants.
Contaminants That Accumulate in Poorly Ventilated Spaces
A primary category of indoor pollutants that build up are Volatile Organic Compounds (VOCs), which are gases emitted from various solids and liquids found in the home or office. Sources include cleaning products, paints, varnishes, adhesives, and new furniture, which release chemicals through off-gassing. Concentrations of many VOCs are often ten times higher indoors than outdoors, and without proper airflow, these levels persist.
Biological contaminants thrive when air exchange is restricted, increasing the risk of infections and allergic reactions. Mold spores, bacteria, and viruses linger longer without dilution from fresh air. Damp areas, such as bathrooms or areas with water damage, promote the growth of mold and mildew, which release spores and toxins into the atmosphere.
Carbon dioxide (\(\text{CO}_2\)), a byproduct of human respiration, serves as a reliable marker for poor ventilation, though it is not typically an infectious contaminant. A lack of fresh air exchange causes this gas to accumulate when people occupy a space. Industry standards often cite a maximum indoor level of 1000 parts per million (ppm); exceeding this threshold signals that other, more harmful pollutants are also being concentrated.
Health Effects and Common Symptoms
Exposure to accumulated indoor contaminants often results in immediate physical reactions. These symptoms include irritation of the eyes, nose, and throat, often caused by high concentrations of VOCs. Headaches, dizziness, and fatigue are also common short-term effects, frequently observed when \(\text{CO}_2\) levels rise significantly above the outdoor baseline.
For individuals with underlying conditions, poor indoor air quality can exacerbate existing respiratory problems and allergies. Exposure to biological pollutants like mold spores and dust mite fragments can trigger allergic rhinitis, coughing, and wheezing, worsening asthma attacks. Long-term exposure to these irritants can also increase the risk of respiratory infections.
A collection of non-specific symptoms linked to time spent in a poorly ventilated building is referred to as Sick Building Syndrome (SBS). Occupants report general discomforts like difficulty concentrating, nausea, and dry or itchy skin. A defining characteristic is that the symptoms typically improve or disappear shortly after the individual leaves the affected building.
Strategies for Improving Indoor Air Quality
The most effective approach to reducing contaminant buildup is to increase the rate of air exchange through improved ventilation. Natural ventilation is achieved by opening windows and doors to allow fresh air to dilute stale air. Mechanical ventilation, such as running exhaust fans in kitchens and bathrooms, actively removes moisture and pollutants directly at their source, which is particularly important during activities like cooking or showering.
Source control involves minimizing the introduction of pollutants into the indoor environment. Consumers can choose low-VOC or zero-VOC alternatives for products like paints, flooring, and household cleaners to reduce chemical off-gassing. Prohibiting indoor smoking and ensuring that gas appliances are properly vented are effective measures for controlling major pollutant sources.
Air filtration plays a supporting role by actively removing particulate matter. High-Efficiency Particulate Air (HEPA) filters capture airborne particles as small as 0.3 microns, including mold spores, dust, and allergens. Activated carbon filters are often used with HEPA filters because they specialize in adsorbing gases, odors, and chemical vapors like VOCs.
Controlling indoor humidity prevents the growth of biological contaminants. Maintaining a relative humidity level between 40% and 60% discourages the proliferation of mold, mildew, and dust mites. Using dehumidifiers in basements and ensuring air conditioning units are properly maintained are important steps in managing moisture.