Air purifier
An air purifier is a device that removes or reduces airborne particles, gases, or other contaminants in an indoor space.
High-efficiency particulate air filter: A mechanical filter that captures airborne particles through a dense mat of fibers, meeting defined efficiency standards. Many purifiers use HEPA filters to trap particles without intentionally producing other substances.
Particulate matter: A mixture of solid particles and liquid droplets suspended in air, classified partly by particle size. Particle size determines how pollutants move indoors and which filtration mechanisms can capture them.
Wildfire smoke: A mixture of gases and fine particles produced by vegetation fires and transported through the atmosphere. Portable particle filtration can reduce indoor smoke particles when outdoor smoke enters a building.
Air ionizer: A device that releases charged ions into air, causing particles to become charged or attach to surfaces. Ionizers may alter particle behavior, but differ from purifiers that capture contaminants in a filter.
Exposure assessment: The estimation of how much of a hazard reaches people through particular routes and over time. A purifier’s value depends on whether it meaningfully changes occupants’ exposure to relevant pollutants.
Activated carbon: A highly porous form of carbon used to adsorb molecules from gases and liquids. Carbon beds can reduce odors and some gaseous pollutants that particle filters do not capture.
Indoor air quality: The condition of air inside buildings, shaped by pollutants, ventilation, humidity, and occupant activities. Purifiers address only some contributors to indoor air quality, alongside source control and ventilation.
Respiratory virus transmission: The spread of viruses through infectious particles emitted from an infected person’s respiratory tract. Filtration can lower concentrations of suspended infectious particles, but does not replace other controls.
Humidifier: A device that adds water vapor to indoor air to raise its relative humidity. Humidifiers change moisture levels rather than directly removing airborne contaminants.
Filter replacement: The removal of a used air-cleaner filter and installation of a fresh one at an appropriate interval. Loaded or neglected filters can reduce airflow and undermine performance.