Acute

Having a rapid onset and following a short but potentially severe course.

Adsorption

The physical process that occurs when liquids, gases, or suspended matter adhere to the surfaces or in the pores of a material.

Air cleaner

A device used to remove particulate or gaseous impurities from the air; examples include electrostatic precipitator, ion generator, ultraviolet germicidal irradiation cleaner, photocatalytic oxidation cleaner, and gas phase air filter.

Air filter

A device that removes particulate material from an airstream, also called an “air cleaner.”

Airflow resistance

See Pressure drop.

Allergen

A chemical or biological substance (e.g., pollen, animal dander, or house dust mite proteins) that can cause an allergic reaction characterized by hypersensitivity (an exaggerated response).

Allergic respiratory disease

Impairment of the normal state of the respiratory system resulting from exposure — usually by inhalation — to an allergen.

Allergy

An exaggerated or pathological reaction to breathing, eating, or touching substances that have no comparable effect on the average individual.

Asthma

A usually chronic inflammatory disorder of the airways characterized by intermittent episodes of wheezing, coughing, and difficulty breathing, sometimes associated with an allergy to inhaled substances.

Bacterial spore

Inactive phase of bacteria, with a thick protective coating that allows the bacteria to survive harsh environmental conditions.

CADR

The Clean Air Delivery Rate (CADR) is the measure of portable room air cleaner performance. This is defined as the measure of the delivery of contaminant-free air by a portable household electric room air cleaner, expressed in cubic feet per minute (cfm). CADRs are always the measurement of a unit’s performance as a complete system.

Chemisorption

A process whereby a chemical substance adheres to a surface through the formation of a chemical bond.

Chronic

Marked by long duration, by frequent recurrence over a long time, and often by slowly progressing seriousness.

Corona discharge

An electrical discharge brought on by the ionization of a fluid surrounding a conductor, which occurs when the potential gradient exceeds a certain value.

Dander

Minute scales of skin. Dander also may contain hair or feathers.

Disinfection

The process of any reduction or prevention of growth in a microbial population with no percentage efficiency specified.

Double-blind study

A type of clinical trial study design in which the study participants and the investigators do not know the identity of the individuals in the intervention and control groups until data collection has been completed.

HEPA filter

High-efficiency particulate air filter. Extended surface mechanical air filter having a minimum particle removal efficiency of 99.97 percent for all particles of 0.3 µm diameter, with high efficiency for both larger and smaller particles.

HVAC

Heating, ventilating, and air conditioning.

IAQ

Indoor air quality.

MERV

Minimum efficiency reporting value.

Mold spore

Tiny reproductive structures produced by vegetative mold.

Ozone

An unstable, poisonous allotrope of oxygen that is formed naturally in the ozone layer from atmospheric oxygen by electric discharge or exposure to ultraviolet radiation, also produced in the lower atmosphere by the photochemical reaction of certain pollutants.

Particulate

A small discrete mass of solid or liquid matter that remains individually dispersed in gas or liquid emissions (usually considered to be an atmospheric pollutant).

PCO

Photocatalytic oxidation.

Placebo effect

A usually, but not necessarily, beneficial effect attributable to an expectation that a treatment will have an effect; an effect that is due to the power of suggestion; a sense of benefit felt by a patient that arises solely from the knowledge that treatment has been given.

Pressure drop

The loss of force applied over a filtering media surface due to resistance to airflow.

Rhinitis

Inflammation of the mucous membrane lining of the nose.

Sorption

The common term used for adsorption.

ULPA

Ultra low penetration air filter. Extended surface mechanical air filter having a minimum particle removal efficiency of 99.999 percent for all particles of 0.3 µm diameter, with high efficiency for both larger and smaller particles.

UV

Ultraviolet.

UVGI

Ultraviolet germicidal irradiation.

VOCs

Volatile organic compounds; chemicals that contain carbon and are vaporous at room temperature and pressure.

Vegetative bacteria and molds

Microorganisms that are in the growth and reproductive phase, i.e., not spores