Materials
Off-Gassing
The release of volatile compounds from a material into the air after installation. Emission rates generally decline over time, but the curve differs by compound and material and can extend well past a move-in date.
In more detail
Off-gassing is the release of volatile compounds from a material into the surrounding air. New materials emit because manufacturing leaves residual monomers, solvents, plasticizers and additives in them, and because some products continue releasing compounds as they cure or degrade.
Emission generally follows a decay curve, and its shape differs by compound and material. Solvent-borne finishes release most of what they will release within days. Adhesives, engineered wood products and some foams emit for considerably longer, and formaldehyde in particular can remain detectable well past a move-in date. Temperature and humidity accelerate emission, which is why a closed house in summer measures higher than the same house in spring.
Emission is characterized in chambers rather than in houses: a specimen is held at controlled temperature, humidity and air exchange, and concentrations are measured at intervals to derive emission factors in µg/m²·h. Those figures describe the material, not the room. What an occupant is exposed to also depends on how much of the material is present and how much outdoor air is diluting it.
Why it matters
Off-gassing peaks exactly when a house is new, which is when people move in — and it is one of the few air quality problems whose magnitude is set by finish selection. Total installed area matters as much as product choice, because flooring, cabinetry, millwork and upholstery cover most of the interior surface. Ventilation is the reliable countermeasure, and running it hard through the first weeks of occupancy is the cheapest intervention available.
The common misunderstanding
That the smell is the measure. Some emitted compounds have no odor and some odorous compounds are innocuous, so a room that smells new is not reliably worse than one that does not. Formaldehyde is the common case: often present without being obvious, which is why emissions from composite wood are regulated rather than left to the nose.
Related terms
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Sources
Last reviewed July 2026 by Compound Editorial. Definitions are educational and not project-specific engineering or medical advice.