According to the United States Environmental Protection Agency (EPA), volatile organic compounds (VOCs) means any compound of carbon, excluding carbon monoxide, carbon dioxide, carbonic acid, metallic carbides or carbonates, and ammonium carbonate, which participates in atmospheric photochemical reactions.
It mainly include hydrocarbons (i.e. the general term of hydrocarbons, which is a compound composed of carbon and hydrogen atoms, mainly including alkanes, cycloalkanes, alkenes, alkynes and aromatic hydrocarbons), halogenated hydrocarbons (i.e. compounds in which hydrogen atoms in hydrocarbon molecules are replaced by halogen atoms), as well as oxygen-containing organic compounds and nitrogen-containing organic compounds, specifically including benzene series (such as toluene and xylene), organic chlorides, organic ketones, acids, esters, alcohols, ethers, amines and hydrocarbon compounds.
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VOCs aren't the only organic matter in the air. Some organic compounds can exist in both air and particulate matter at room temperature, and the proportion of the two will change with the change of temperature. Such organic compounds are called semi-volatile organic compounds, or SVOCs for short.
Some organic compounds only exist in particulate matter at room temperature, and they belong to non-volatile organic compounds, referred to as NVOCs.
Whether VOCs, SVOCs or NVOCs are involved in atmospheric chemical and physical processes, and some of them can directly harm human health. They bring environmental effects including affecting air quality, weather and climate, etc.
What Are the Sources of VOCs?
VOCs can be found in the air both indoors and outdoors. Some of these sources continue to produce VOCs when stored or transported. Some of the more common VOCs include benzene, formaldehyde, and toluene.
Indoor Sources
Construction Materials:
- Paint and paint remover
- Varnish and finish
- Caulking materials and sealants
- Adhesive
- Floor, carpet and artificial wood products
Home and Personal Care Products:
- Detergents and disinfectants
- Furniture
- Pesticides
- Air freshener
- Cosmetics and deodorants
- Fuel oil and gasoline
Others:
- Tobacco smoke
- Dry cleaned clothes
- Arts and crafts
- Wood burner
- Printers and copiers
Outdoor Sources
- Gasoline emissions
- Diesel emissions
- Burning woods
- Exploitation and processing of oil and natural gas
- Industrial emissions
What Are the Harms of VOCs?
VOCs are important precursors of ground-level ozone and PM2.5, which are the main culprits of haze.
At the same time, it can also react with other pollutants like NOx and SOx to generate photochemical pollutants, which can cause more serious secondary harm to the environment.
Source: worldatlas.com
1. Unpleasant smell: VOCs are air pollutant that endangers human health. They are often accompanied by peculiar smell and malodor, which are harmful to respiratory system.
2. Harmful to ecosystem: VOCs will cause great harm to the balance of the ecosystem. For example, volatile organic compounds of halogenated hydrocarbons will exist in the atmosphere for a long time. Once they diffuse to the ozone layer, they will react with O3, eventually reducing O3 concentration and forming ozone hole.
In addition, some hydrocarbon pollutants will react with NOx through sunlight, and become photochemical smog under certain specific meteorological conditions and special geographical environment.
Most VOCs are flammable and explosive, and high concentration will cause fire and explosion.
VOCs are the main precursor of PM2.5, which can be converted into PM2.5 in the air. At the same time, when PM2.5 meets O3, VOCs and other substances, chemical reactions occur, forming a haze weather.
3. Carcinogenic, teratogenic, mutagenic: VOCs are usually carcinogenic, teratogenic and mutagenic because of their variety and complex composition, which are easy to cause temporary or permanent damage to the human nervous system, internal organs and blood system.
Specific symptoms are as follows:
- Cough, throat congestion and dyspnea
- Tears, blurred vision and skin irritation
- Leukemia, liver function decline, memory decline
Source: healthline.com
How to Reduce VOCs in Your Home?
- Source and Process Control
It is mainly through the change of raw materials, the use of advanced equipment, the improvement of process flow, as well as the control of process conditions to inhibit the generation of VOCs.
For example:
- When using products with high levels of VOCs, it's necessary to open the window to speed up air flow.
- Before installing new carpets or building products, expose them to the outdoors to release VOCs.
- Do not store products containing VOCs indoors, including in garages connected to the house.
- End Treatment
It mainly deals with the VOCs generated, including recycling method and destruction method.
The recycling method can realize the recycling of VOCs, mainly including condensation method, adsorption method, and membrane separation method.
Among them, the air purifier which equipped with absorption filter like activated carbon, can effectively absorb VOCs at home.
The destruction method is to convert it into pollution-free carbon dioxide and water by biological or chemical means, mainly through combustion, photocatalysis, ozonation, low-temperature plasma, etc.
Reference
1. C. Yang, G. Miao, Y. Pi, Q. Xia, J. Wu, Z. Li, J. Xiao, Abatement of various types of VOCs by adsorption/catalytic oxidation: A review, Chem. Eng. J., 370 (2019) 1128-1153.
2. C. He, J. Cheng, X. Zhang, M. Douthwaite, S. Pattisson, Z. Hao, Recent Advances in the Catalytic Oxidation of Volatile Organic Compounds: A Review Based on Pollutant Sorts and Sources, Chem. Rev., 119 (2019) 4471-4568.
3. A. Kansal, Sources and reactivity of NMHCs and VOCs in the atmosphere: a review, J. Hazard. Mater., 166 (2009) 17-26.