Indoor air quality is one of the most important considerations when it comes to ensuring health and safety in built environments. Building owners and managers need to guarantee the provision of fresh air and that air pollutants are always controlled. One group of air pollutants that we should put focus on is total volatile organic compounds (TVOCs)
What are volatile organic compounds?
VOCs are a group of chemicals that have a high vapor pressure and low boiling point, meaning that they easily evaporate and become airborne at room temperature.
The European Union (EU) thus defines VOCs as any organic compound with an initial boiling point that is less than or equal to 250°C at an atmospheric pressure of 101.3 kPa.
VOCs can classified into three types:
Very volatile organic compounds (VVOCs)
VVOCs have a boiling point ranging from <0 to 50-100 degrees centigrade. Due to their high volatility, VVOCs commonly exist as a gas. Examples of VVOCs are:
- Methyl Chloride
Semi-volatile organic compounds (SVOCs)
SVOCs have a boiling point range of 240-260 to 380-400 degrees centigrade. While SVOCs are less volatile, this does not mean that they should not be controlled. Examples include:
- Pesticides (DDT, Chlordane, Plasticizers (Phthalates)
- Fire retardants (PCBs, PBB)
Volatile organic compounds (VOCs)
These compounds have a boiling point ranging from 50-100 to 240-260 degrees centigrade. While the term VOCs is commonly used to describe all types of volatile organic compounds, only the ones that are able to vaporize at the given temperature ranges are considered VOCs. Examples of VOCs are:
- Ethanol (Ethyl Alcohol)
- 2-propanol (Isopropyl Alcohol)
Total volatile organic compounds, defined
Total volatile organic compounds (TVOCs) is the term used to describe the sum of all the volatile organic compounds (VOCs). Since there are a wide range of VOCs, it is somehow impossible to monitor all of them continuously. Thus, the term TVOCs was adopted to measure the total amount of volatile organic compounds in a given environment.
Acceptable indoor TVOC levels
The acceptable indoor TVOC (Total Volatile Organic Compounds) levels vary depending on the specific guideline or standard used. But, the 500 ug/m3 indoor TVOC level is commonly encountered across various standards and can be considered as a basis. For example:
- RESET sets acceptable indoor TVOC levels at <500 ug/m3 and <400 ug/m3 for high performance.
- The Enhanced Indoor Air Quality Testing and Monitoring Protocol from Fitwel (PDF) also mentions levels of less than 500 ug/m3
- The International WELL Building Institute (IWBI) sets a guideline of 500 µg/m³ for TVOCs in indoor air.
Sources of VOCs
Volatile organic compounds can come from a wide variety of sources. Indoors, sources of VOCs include:
- Flooring materials
- Air fresheners
- Tobacco smoke
- Outdoor sources, such as vehicle exhaust and industrial emissions that can enter indoors.
Are all VOCs harmful?
The answer is that it depends.
The potential health and environmental effects of VOCs depend on the specific compound, its concentration, the vulnerability of the person, and the duration of exposure. Infants, young children, pregnant women, and individuals with pre-existing health conditions may be more vulnerable to the adverse effects of VOCs.
Some VOCs are considered hazardous air pollutants (HAPs). Examples of these VOCs include benzene, formaldehyde, and perchloroethylene. These have been shown to cause cancer, reproductive and developmental problems, and other serious health effects. Other VOCs can cause milder health effects, such as eye, nose, and throat irritation, headaches, and dizziness. These effects may be short-term and reversible.
How do TVOCs affect indoor air quality?
TVOC (Total Volatile Organic Compounds) can affect indoor air quality in several ways:
- Health effects
As mentioned above, exposure to VOCs can cause a range of health effects, such as eye, nose, and throat irritation, headaches, dizziness, and respiratory problems. Long-term exposure to certain VOCs, such as benzene, formaldehyde, and trichloroethylene, may increase the risk of cancer.
TVOCs can produce unpleasant odors, which can be a source of discomfort and may indicate poor indoor air quality.
- Building performance
TVOCs can affect the performance of building materials, such as paints, coatings, and adhesives, leading to premature deterioration and reduced lifespan.
- Energy efficiency
High levels of TVOCs can increase the energy needed for heating, ventilation, and air conditioning (HVAC) systems to maintain a comfortable indoor environment, leading to higher energy costs and greenhouse gas emissions.
To maintain good indoor air quality, it’s important to monitor and control the levels of TVOCs in indoor environments. Some of the strategies to perform are:
- Ensuring ventilation
Adequate ventilation can help remove pollutants from indoor air, including TVOCs. This can be achieved by opening windows, using exhaust fans, or installing a mechanical ventilation system.
- Source control
Identifying and controlling the sources of TVOCs can be an effective way to reduce their levels indoors. This can be done by choosing low-emitting products and materials, minimizing the use of products that emit VOCs, and avoiding smoking indoors.
- Installation of air purifiers
Air purifiers with activated carbon filters can help remove TVOCs from indoor air by adsorbing them onto the surface of the filter.
- Regular cleaning
Regular cleaning of indoor surfaces can help reduce the buildup of dust and other particles that may contain TVOCs.
- Humidity control
High humidity levels can increase the emissions of TVOCs from building materials and furnishings. Maintaining indoor humidity levels between 30-60% can help control the emission of TVOCs.
- Putting attention to outdoor air quality
The quality of outdoor air can significantly impact indoor air quality. Keeping windows closed during high pollution periods, avoiding outdoor activities during peak traffic hours, and planting air-purifying plants can help reduce exposure to outdoor pollutants that may contain TVOCs.
- Air quality monitoring
Indoor air quality monitoring can provide a more detailed analysis of TVOC levels, as well as other pollutants and factors that may impact indoor air quality. By continuously monitoring the air, building managers can measure the effectiveness of their air quality strategies and make adjustments based on the readings.