True HEPA – A consumer air filter labelled True HEPA should conform the closest to the DOE standard for a HEPA air filter. At its highest efficiency, it should remove 99.97 percent of all particles that are 0.3 microns in size.

Volatile Organic Compounds (VOCs) are a large group of chemicals that are found in many products we use to build and maintain our homes. Once these chemicals are in our homes, they are released or “off-gas” into the indoor air we breathe.

The Clean Air Delivery Rate, or CADR, on a box can tell a consumer how efficient air purifiers are at removing a certain contaminant from the indoors. The three pollutants that are measured are pollen, smoke and dust. These three pollutants are the most common ones found in the home's indoor air.

CFM is an abbreviation for cubic feet per minute (cu ft/min). When used in the context of a particle counter's flow rate, it is a measurement of the velocity at which air flows into the sample probe.

Particulate matter sensor PM 2.5. ➔Monitors and controls the concentration of particulate matter precisely. ➔ Based on the optical principle of scattered light for particle detection.

Carbon dioxide is a colourless gas formed during the combustion of any material containing carbon and an important green house gas. Sources of CO2: ➔ All energy production using combustion emits carbon dioxide.