What Are VOCs, and Should You Worry About Them at Home?

Volatile organic compounds (VOCs) are carbon-based chemicals that evaporate at room temperature, given off by paints, cleaning products, air fresheners, furniture, building materials, and cooking. Some are harmless at the levels found in homes and some aren’t, and a single “total VOC” number can’t tell them apart. There’s no health-based limit for total VOCs. Formaldehyde is different: it’s one VOC with clear guidelines, the World Health Organization’s (WHO) 0.1 mg/m³ (about 80 ppb) over any 30 minutes, and it’s the one most worth measuring on its own.

This article is general information, not medical advice.

Why Indoors Matters

The US Environmental Protection Agency (EPA) notes that concentrations of many VOCs are consistently higher indoors than outdoors, up to ten times higher, and its TEAM studies found about a dozen common organic pollutants at 2 to 5 times outdoor levels inside homes, rural or industrial. While you use a product that contains them, such as paint stripper, levels can be far higher. The EPA also notes that no federally enforceable standards have been set for VOCs in non-industrial settings.

The Trouble With “Total VOC”

A total VOC (TVOC) reading adds up many different compounds as if they were one. A monitor reporting 500 ppb could be seeing mostly ethanol from hand sanitiser, which matters little, or a compound that matters more; the number can’t say which. And low-cost monitors usually measure it with metal-oxide sensors, which respond differently to different compounds and drift with temperature and humidity:

• In a 2024 co-location study of 87 low-cost indoor monitors, Manu and colleagues found that the TVOC sensors deviated by up to 79% from reference instruments, far more than the ±20% their makers stated, while the same monitors’ CO₂, temperature, and humidity sensors met their specifications.
• Monitors also report TVOC in different ways, in ppb, in µg/m³, or as an index of their own, so two brands’ numbers aren’t comparable.

So read TVOC as a relative signal: whether today is higher than usual, and what you were doing when it jumped. A rise after cleaning, painting, or cooking is a reason to ventilate.

Formaldehyde

The US National Cancer Institute names pressed-wood products containing formaldehyde resins, such as particleboard, plywood, and fiberboard, as often a significant source in homes, along with glues, permanent-press fabrics, cigarette smoke, and unvented fuel-burning appliances such as gas stoves. Formaldehyde irritates the eyes, nose, and throat, and the International Agency for Research on Cancer (IARC) classifies it as a human carcinogen; the cancer evidence comes mostly from workers exposed to far higher levels than homes.

Source	Limit
WHO indoor air quality guidelines (2010)	0.1 mg/m³ (about 80 ppb) for any 30-minute period, set to prevent sensory irritation and meant to protect over a lifetime
Health Canada, residential indoor air	123 µg/m³ (100 ppb) over 1 hour; 50 µg/m³ (40 ppb) over 8 hours

In a 2017 review of the newer cancer studies, Nielsen and colleagues concluded that the WHO guideline’s credibility hasn’t been challenged: at its level, the airway inflammation and irritation that could lead to harm are prevented. Heat and humidity raise how much formaldehyde materials give off.

Reducing VOCs and Formaldehyde

• Ventilate, especially while using products that give off VOCs, and follow their labels.
• Remove the source where you can; the EPA suggests a sealant on the exposed surfaces of panelling and other furnishings when you can’t.
• Ask about formaldehyde content when buying pressed-wood furniture, cabinets, and building materials, as the National Cancer Institute suggests.
• Keep temperature and humidity moderate, which the National Cancer Institute also advises, since materials give off formaldehyde faster when it’s warm and humid. See What’s the Right Humidity at Home?

Following It in Kaizora

Total VOC Concentration and Formaldehyde Concentration are air quality metrics on Air Quality, kept in parts per billion. Readings are logged by hand, each at a known position, since no importer brings them yet; log a monitor’s TVOC only if it reports it in ppb, not as an index. Your exposure joins readings with your location history: at each of your location fixes, your value is the newest reading within 100 metres in the hour before. A reference range you add on Formaldehyde Concentration, such as a band above 80 ppb, flags readings over the WHO’s guideline. See Read the Air Quality Page and Your Exposure.

The Short Version

• VOCs are many different chemicals, often higher indoors than out.
• Total VOC has no health limit, and low-cost sensors measure it poorly; read it as a relative signal.
• Formaldehyde has clear guidelines: the WHO’s is 0.1 mg/m³ (about 80 ppb) over 30 minutes.
• Ventilate, remove sources, and keep the air moderately cool and dry.

Sources

• US Environmental Protection Agency, Volatile Organic Compounds’ Impact on Indoor Air Quality.
• Manu S et al., “A co-location study of 87 low-cost environmental monitors: assessing outliers, variability, and uncertainty,” Buildings 14, no. 9 (2024): 2965. doi:10.3390/buildings14092965
• World Health Organization, WHO guidelines for indoor air quality: selected pollutants (2010).
• Nielsen GD, Larsen ST, and Wolkoff P, “Re-evaluation of the WHO (2010) formaldehyde indoor air quality guideline for cancer risk assessment,” Archives of Toxicology 91, no. 1 (2017): 35–61. doi:10.1007/s00204-016-1733-8
• Health Canada, Residential Indoor Air Quality Guidelines.
• US National Cancer Institute, Formaldehyde and Cancer Risk.