Off-gassing describes the process where manufactured materials release airborne chemicals from their solid or liquid form into the surrounding air. This release is often noticeable as the characteristic “new” smell associated with items like fresh paint, new cars, or new furniture. While this scent may initially seem like a sign of newness, it is actually an indication of chemicals evaporating and dispersing into the environment. The process of off-gassing is a common contributor to indoor air quality issues, as these released compounds can accumulate in enclosed spaces.
The Mechanism of Off-Gassing
The physical release of these chemicals is governed by principles of vapor pressure and diffusion. A substance with a high vapor pressure has a strong tendency to evaporate, meaning its molecules readily escape from the liquid or solid phase into the gas phase, even at room temperature. The chemicals used in manufacturing, such as solvents and binders, possess this high vapor pressure, making them volatile.
The rate at which a chemical off-gasses is heavily influenced by temperature. Higher temperatures increase the kinetic energy of the chemical molecules, which accelerates the rate of evaporation. The diffusion of these gaseous molecules from inside the material to the surface also plays a role. Off-gassing is a continuous process that is highest when the product is new and gradually decreases over time, sometimes lasting for months or years, as the material “cures” or fully dries.
Volatile Organic Compounds
The primary chemical species involved in this release are known as Volatile Organic Compounds, or VOCs. These are carbon-containing chemicals with a low boiling point and a high vapor pressure, which allows them to easily evaporate into the air. The concentration of these compounds is consistently measured at levels up to ten times higher indoors than outdoors, largely due to off-gassing and limited air exchange.
Examples of VOCs frequently released include formaldehyde, a component of adhesives in pressed wood products, and benzene and toluene, often found in paints and solvents. While a strong odor signals off-gassing, many VOCs are odorless yet still present. A related group, Semi-Volatile Organic Compounds (SVOCs), have a lower vapor pressure and off-gas more slowly, meaning their release can persist for an extended duration.
Common Off-Gassing Sources in the Home
A wide variety of everyday household items and building materials are sources of off-gassing, contributing to the overall chemical load in indoor air. New furniture, especially pieces made from composite materials like particleboard and medium-density fiberboard (MDF), releases VOCs like formaldehyde from the resins and adhesives used in construction. Upholstered items and mattresses, particularly those made with synthetic foams, can off-gas chemicals from flame retardants and polyurethane.
Building and renovation materials are a major category of sources. Fresh paint, lacquers, varnishes, sealants, and adhesives contain organic solvents that evaporate into the air over time. New flooring, such as synthetic carpets, vinyl, and laminate, can release VOCs from the synthetic fibers, dyes, and installation glues. Even common household products, including cleaning supplies, disinfectants, and air fresheners, contain and release VOCs during use and storage.
Reducing Exposure and Improving Air Quality
Minimizing exposure to off-gassing chemicals involves practical steps focused on source control and ventilation. When purchasing new items, selecting products with low-VOC or zero-VOC certifications, such as paints, sealants, and furniture, significantly reduces the initial chemical burden. These certifications indicate that the product meets stringent standards for low chemical emissions.
Maximizing ventilation is a highly effective strategy, particularly when new items are introduced or during renovation projects. Airing out new furniture, carpets, or building materials in a well-ventilated space, or outdoors for a period, allows the most intense initial off-gassing to occur away from living areas. Air purification systems that utilize activated carbon filters can also help, as carbon is effective at adsorbing gaseous chemicals like VOCs from the air.