VOCs: what they are, where they come from, and how to measure them

VOCs are among the prime targets for IAQ professionals, alongside viruses, bacteria, particles and certain gases, which can become toxic at excessively high concentrations. The aim is to keep airborne concentrations of these substances to a minimum. And the key weapon in this fight is something we’ve discussed at length in other INsights blog articles: the air change rate (or ACR for short), using CO2 concentration as a particularly effective indicator.

What are volatile organic compounds?

VOCs are a large group of chemicals that can easily be emitted as gases into the air. To qualify as a VOC, a substance has to be volatile – in other words, the molecules evaporate or sublimate under standard temperature, humidity, light (UV) and pressure conditions. The term therefore covers a relatively broad spectrum of compounds, whose origins can be either artificial (evaporation of solvents, chemicals, etc.) or natural (emitted by plants, through fermentation, etc.).

For IAQ professionals, the most important VOCs are chemicals that are easily emitted as gases under ambient conditions, thereby building up in the air inside a building. The main sources of these substances are as follows:

• Cleaning and maintenance products: certain household products, such as detergents, cleaning products and air fresheners.
• Building and finishing materials: certain materials such as paints, varnishes, adhesives and carpets.
• Furniture and household items: certain objects such as mattresses, cushions and toys.
• Electronic devices such as printers and computers.
• Heating equipment such as ovens and wood-burning stoves.
• Activities such as smoking, cooking and welding.

Although each of these sources only emits tiny quantities of VOCs, the build-up of these compounds from different origins can leading to worryingly high overall concentrations – expressed as total volatile organic compounds, or TVOCs – in indoor air.

Among the many VOCs found in the atmosphere, those listed below are among the most commonly encountered in the world of IAQ:

Are VOCs toxic?

Given the sheer size of VOCs as a group, it’s hard to make generalisations. But many VOCs can be harmful to health. The effect varies according to VOC type, concentration and exposure time. Once again, the real problem stems from a build-up of multiple VOCs in a poorly ventilated room.

The potential harm caused by VOCs also varies dramatically between individuals. Some people will experience symptoms more quickly than others, or will be more susceptible to the harmful health effects of particular compounds. Here too, it’s important to think about the risk posed by VOCs holistically, which implies monitoring all such compounds accumulated in the air and considering their combined potential toxicity to the exposed population as a whole.

The effects of VOCs also vary significantly, from benign symptoms such as fatigue and irritation of the eyes, airway and skin, to serious problems such as cancer and respiratory problems following prolonged exposure.

As we explain in this article, the danger thresholds for concentrations of TVOCs are as follows (expressed in parts per billion):

In short, the risks posed by VOCs are just as volatile as the compounds themselves!

How to protect against VOCs

The best way to protect against VOCs is to act early: prevention is always the best option. There are several easy ways to avoid these compounds building up in the ambient air and to reduce their concentrations.

As with other types of indoor air pollution, the most reliable and effective method is to make sure the space is well-ventilated: regularly let fresh air into the room to dilute VOC concentrations, or make sure the building’s ventilation system guarantees a sufficient ACR. Ventilation system professionals routinely check the ACR, using instruments such as the DBM 620 air flow meter and portable anemometers to adjust the air flows into and out of a room, taking into account the total volume of the space, how many occupants are inside and what they’re doing.

While intense physical exercise can release varying quantities of CO2 into the air, other professional and business-related activities can also emit VOCs, depending on what equipment is in the room and how it’s being used. Some mission-critical production and storage areas will therefore require a higher ACR than basic office spaces.