Volatile organic compounds (VOCs) are found virtually everywhere, but concentrations are consistently higher indoors than outdoors. An EPA survey of 56 buildings found that every detectable VOC had a median indoor concentration at least twice the outdoor level, and five common compounds were found at concentrations ten times higher inside than outside. Your home, your workplace, your car, and the outdoor air all contain VOCs, though the specific compounds and their sources differ by setting.
What VOCs Actually Are
VOCs are carbon-based chemicals that evaporate easily at room temperature. That evaporation is what makes them so widespread: they move from solid or liquid products into the air you breathe. The most common ones include formaldehyde, benzene, toluene, xylene, acetone, and isopropyl alcohol. Some have a noticeable smell (think fresh paint or gasoline), while others are odorless. Their boiling points generally range from about 50°C to 260°C, which means they readily become gases in typical indoor and outdoor conditions.
Inside Your Home
The largest everyday source of VOC exposure for most people is their own house. These compounds come from a surprisingly long list of household products and materials, often releasing chemicals both during use and while sitting in storage.
Paints, varnishes, and wood stains are some of the most familiar sources. Paint strippers and adhesive removers contain methylene chloride, a particularly potent VOC. But the list extends well beyond renovation products: cleaning sprays, disinfectants, air fresheners, moth repellents, aerosol cans of any kind, pesticides, hobby supplies like glues and markers, and even dry-cleaned clothing all release VOCs into your indoor air.
Stored fuels and automotive products are another major contributor, especially in attached garages. Benzene, one of the more concerning VOCs from a health standpoint, enters homes primarily through tobacco smoke, stored fuels, paint supplies, and car exhaust that drifts in from an attached garage.
Cosmetics and personal care products round out the indoor picture. Degreasing agents, nail polish, hair spray, and perfumes all contain organic solvents that evaporate into your living space.
New Buildings and Furniture
If you’ve ever noticed a strong chemical smell in a newly built home or a freshly furnished room, that’s VOC off-gassing. New construction materials, engineered wood products like particleboard, adhesives, carpeting, and sealants all release VOCs at their highest rates when they’re brand new.
Research tracking VOC levels in new homes over three years found that concentrations decrease dramatically during the first year and eventually settle near the levels seen in older homes. The steepest drop happens in the initial months. However, not all compounds follow that pattern. Formaldehyde and a compound called alpha-pinene, both associated with wood-based building materials, take significantly longer to flush out, particularly in wood-framed houses. If you’re moving into new construction, keeping windows open and ventilating aggressively during those first months makes a measurable difference.
Outdoor Air
Outside, the biggest sources of VOCs are vehicle exhaust and fuel systems. Cars release VOCs both through incomplete combustion of gasoline and through simple evaporation from fuel tanks and filling stations. The IPCC identifies motor vehicle emissions and biomass burning (wildfires, agricultural burns) as the two largest anthropogenic sources of outdoor VOCs globally.
Industrial processes contribute as well. Fuel production and distribution facilities, chemical manufacturing plants, and refineries all emit VOCs. These anthropogenic emissions are concentrated in heavily industrialized regions, with 95% occurring in the Northern Hemisphere and peaking between 40°N and 50°N latitude. That band covers much of the United States, Europe, and East Asia.
Nature produces VOCs too. Trees and plants emit organic compounds like isoprene and monoterpenes, especially in warm, sunny conditions. That pine-forest smell or the scent of eucalyptus is literally plant-produced VOCs entering the air. Globally, natural emissions from vegetation actually exceed human-made ones, but they’re spread across forests and rural areas where their health impact is lower. In cities and suburbs, the human-made sources dominate.
High-Exposure Workplaces
Certain jobs carry much higher VOC exposure than typical indoor environments. The dry cleaning industry has long been flagged as one of the highest-risk settings. When OSHA surveyed state consultation programs in 1988 to identify the riskiest small businesses, dry cleaners ranked second, behind only auto body repair shops. NIOSH evaluations found that workers were exposed to high levels of perchloroethylene, the primary dry cleaning solvent.
Auto body and paint shops, printing facilities, nail salons, manufacturing plants that use solvents, and petroleum refineries all expose workers to elevated VOC levels on a daily basis. The exposure is often a combination of direct contact with liquid solvents and inhalation of vapors in enclosed spaces with limited ventilation.
Why Indoor Levels Are So Much Higher
The EPA’s Building Assessment Survey measured individual VOC concentrations in 56 office buildings and compared indoor levels to outdoor levels at each site. The results were striking: 27 different VOCs had median indoor concentrations more than double the outdoor level. Five compounds, including limonene (common in cleaning products and air fresheners), hexanal (released by wood and linoleum), and several hydrocarbons from building materials, had indoor levels roughly ten times the outdoor concentration or higher.
The reason is straightforward. Indoor spaces trap emissions from dozens of products and materials in a relatively small volume of air. Without active ventilation, those compounds accumulate. Outdoor air, by contrast, disperses VOCs across an enormous volume and breaks them down through sunlight-driven chemical reactions.
Reducing Your Exposure
Ventilation is the simplest and most effective strategy. Opening windows, running exhaust fans, and allowing new products to off-gas in well-ventilated spaces before bringing them into closed rooms all help. Choosing low-VOC or no-VOC paints, adhesives, and cleaning products cuts emissions at the source.
For air filtration, activated carbon filters are the most reliable technology for removing gaseous VOCs. Standard HEPA filters excel at trapping particles like dust and pollen but do little against gases. An MIT study evaluating several indoor air cleaners found that devices relying on chemical reactions to neutralize VOCs performed poorly. The cleaners that actually worked were using physical sorbent filters (activated carbon) to absorb the compounds. The researchers’ recommendation: stick with activated carbon filtration rather than devices that claim to chemically destroy VOCs.
Storing fuels, solvents, paints, and automotive chemicals in a detached garage or shed rather than inside your living space also makes a notable difference, since these products release VOCs even when their containers are sealed.