Indoor Air Quality | Ventilation and VOCs
Updated: Nov 3, 2019
Indoor air quality related complaints have traditionally been associated with older and poorly maintained buildings. Increasingly however, the presence of numerous sources of synthetic chemicals has resulted in elevated concentrations of volatile organic compounds (VOCs) in recently renovated or newly constructed airtight buildings. Poorly ventilated buildings can affect your health, cognitive function, productivity and can even contribute to the spread of disease from viruses and bacteria.
What Are VOCs?
Volatile organic compounds (VOCs) are organic chemicals that evaporate easily to become vapors or gases. VOCs are some of the most common indoor air pollutants, particularly in new homes, and can originate from a variety of sources. They can be released into indoor environments from cleaning and disinfecting products, wax, paints, varnish, wood preservatives, carpeting, furniture, building materials, copier machines, aerosol sprays, pesticides, moth repellants, air fresheners, perfumes, cosmetics, dry cleaned clothing, adhesives, microbial growth, hobby products, cooking, cigarettes and a host of other sources. The amount of VOCs emitted from products tends to decrease as the product ages, but may remain at harmful levels
How Effective are HRV Units?
Although reducing outdoor air exchange rates has improved energy conservation, the build-up of VOC concentrations “off-gassing” the toxins that a product emits into the air can become elevated. The 12-hour trending graph below monitors the total VOCs in a home. The HRV unit was enabled at the beginning of the trend and demonstrates the effectiveness of mechanical ventilation, another approach to reduce exposure to these toxins.
Measuring VOCs in the Air
One method of measuring VOCs is by using a photo-ionization detector. This estimates the total VOCs (TVOC) and provides immediate results, but is unable to distinguish or identify individual VOCs. TVOC results can be used to surmise that VOCs are generally present in indoor air, possibly indicating poor IAQ.
Health Effects of VOCs
As with other pollutants, the extent and nature of the health effects will depend on many factors including level of exposure and length of time exposed. In sufficient quantities, some VOCs can cause eye, nose, and throat irritation; headaches, loss of coordination, dizziness, nausea, skin irritation and difficulty breathing. Hypersensitive individuals can have severe reactions to VOCs at low concentrations.
How Do I Reduce Exposure to VOCs?
The best way to avoid VOCs is to not introduce them in the first place. Whenever possible use products labeled “No VOC / Low VOC”. Minimize the use of scented products such as plug-in or aerosol deodorizers, candles and incense. Store products in a separate room like an outdoor shed or in areas with proper ventilation. If you have no choice and are in a situation where you are exposed to VOCs you can increase the ventilation to dilute the containment.
How long does it take to flush out pollutants in a home using an HRV ?
Dilution is the solution to pollution. This study was performed in a 3200 sq/ft residential home built in 2006 while operating a newly installed 200 cfm heat recovery ventilator unit (HRV) on high speed and furnace fan operating in manual mode. The trending graph above displays that prior to the HRV start-up, TVOC levels were about 900 μg/m3 and CO2 levels at 1050 ppm. After 12 hours of HRV operation, TVOC concentrations decreased below 200 μg/m3 and CO2 levels fell below 700 ppm.