TVOC/VOCs

Sources of Volatile Organic Compounds (VOCs)

A volatile organic compound is a broad term which refers to a group of organic chemicals (hydrocarbons, aldehydes, ketones, esters, alcohols, acids) which quickly evaporate into the air and have low solubility in water.

Naturally occurring VOCs are extremely common, mostly emitted by plants, animals and microorganisms. However, due to the presence of numerous indoor sources, VOCs are consistently higher in indoor air than outdoors. Some common indoor sources of VOCs include: paints, varnishes, household cleaners and disinfectants, fuels and solvents, building materials (e.g., carpets, furniture, insulation material), tobacco smoke, and cooking activities.

Generally, TVOC concentrations indoors increase in the summer months due to diffusion rates increasing with temperature. 

Commonly perceived as a pleasant scent, TVOCs are key ingredients in many perfumes and are responsible for the 'new car smell'. As TVOCs are commonly released from new materials, increased concentrations are found in new cars or indoor renovations/new builds.

VOCs can even be emitted from human breath and skin. Oxidants within the air (Ozone or hydroxyl radicals) can produce VOCs on the surface of human skin, which can continue to generate VOCs even after an individual has left the indoor environment.

VOC emissions can also vary depending on an individual's choices of food, alcohol, and personal care products (e.g., perfume, deodorant). This type of emission falls under the umbrella term "Bio-effluence", in which pollutants are produced during the metabolic processes that take place within the human body.

There are thousands of VOCs -- making it practically impossible to monitor them all -- which is why we use TVOCs as a metric. TVOC aggregates the concentrations of various VOCs into a single value. No universally agreed-upon definition explains which VOCs are included in the aggregate, so standards must be explored and decided upon before drawing accurate comparisons about TVOC levels across multiple samples.

Typical Sources of Indoor Volatile Organic Compounds

• Solvents, Glues, Disinfectants, Paints, Varnishes
• Plastics, Fabrics, Fibreboard, Insulating Material, Consumer products
• Vehicle Exhausts, Fuel tanks, Cigarette Smoking, Cooking Activities
• Cows, Plants, Forest Fires, Microorganisms

Impacts of Indoor VOCs

Some VOCs can cause distinct, immediate symptoms like irritation of the sensory, respiratory, allergic, and ENT systems. Depending on the dose and length of exposure, humans can experience headaches, loss of coordination, and nausea. VOCs can sometimes cause damage to the liver, kidneys, and central nervous system. Certain VOCs are known to be carcinogenic, such as benzene, methylene chloride, and perchloroethylene, and as a result are particularly toxic.

Common Impacts of VOCs

• Carcinogenic
• Respiratory and ENT Irritants
• Headaches, Loss of Focus
• Kidney, Liver and Central Nervous System Damage

Testing for VOCs

For VOCs, we use metric TVOCs (Total Volatile Organic Compounds). This aggregates all VOCs into one metric. Tenax TA tubes are used, which is a porous polymer adsorbent useful for trapping VOCs. We can use either passive sampling, which takes a period of 2 weeks, or active (pumped) sampling, which takes an hour. Pumped sampling produces a high-pitched buzzing noise when in use.

• Pumped Active Sampling
• Passive Diffusive Sampling
  

Concentrations (normally in µg/m³ ) of TVOCs are lower than levels outlined in the appropriate legislation, depending on the environmental type and activities performed in said environment. Commonly, BREEAM's sustainable building limit is used, being <300µg/m³ over 8 hours.

• The BREEAM limit is <300µg/m³ over an 8-hour period
• The Fitwell limit is <500 μg/m³
• The WELL limit is <500 μg/m³ average over a month for at least 90% of regularly occupied hours for all sensors