Air Cleaning Effects on Health and Perceived Air Quality

Supporting Information

Table 2. Technologies commonly used for gaseous pollutant air cleaning.

Technology Description
& Principles
Advantages Disadvantages Common Applications Related
Health Data

Sorbents

Gaseous pollutants adsorb on porous granular media or condense in pores of media

Many types of sorbents with activated carbon most commonly used

Widely available technology

Can remove broad range of gaseous pollutants with moderate to high efficiency

Pollutants can be released from sorbent into indoor air

Low effectiveness for low molecular weight pollutants including formaldehyde

Must periodically replace sorbent

Sorbent lifetime for indoor air applications not well understood

Large amount of sorbent needed for long lifetime

High sorbent cost

Often high airflow resistance increasing fan energy use

Installed in heating, ventilating and air conditioning systems or in stand-alone portable air cleaners

Minimal data available

Chemisorbents

Gaseous pollutants adsorb on and chemically react with porous granular media

Widely available technology

Can remove broad range of gaseous pollutants with moderate to high efficiency

High chemisorbent cost

Often high airflow resistance increasing fan energy use

Installed in heating, ventilating and air conditioning systems or in stand-alone portable air cleaners

Minimal data available

Photocatalytic oxidation

Gaseous pollutants adsorb on a surface coated with a photocatalyst that is irradiated with a light source, usually a source of ultraviolet light; some adsorbed pollutants decompose

Can remove a range of gaseous pollutants

Usually lower airflow resistance than sorbents and chemisorbents, thus, lower fan energy consumption

Can destroy some bioaerosols

Many systems have low pollutant removal efficiency

Lamp energy use

Cost of periodically replacing lamps

Photocatalysts become inactive, with unknown photocatalyst life

Incomplete breakdown of some pollutants can result in formation of new pollutants potentially harmful to health

Installed in heating, ventilating and air conditioning systems or in stand-alone portable air cleaners

Minimal data available

Ozone generators

Ozone generated and released into indoor air can react with and breakdown some airborne volatile organic compounds

Quiet and energy efficient

Releases ozone into indoor air and ozone is a harmful pollutant

Generally ineffective in significantly reducing airborne volatile organic compounds unless ozone concentrations are very high

Reactions of ozone with airborne volatile organic compounds can lead to production of formaldehyde and ultrafine particles that pose health risks

Usual application is a standalone portable air cleaner

No direct measured data on how these devices affect health; however, ozone generators can raise indoor ozone above levels known to be harmful to health

Plasma air cleaners

Radicals (small reactive molecules) created by electric discharge can oxidize and decompose volatile organic compounds and nitrogen oxides

Quiet and energy efficient

May improve particle removal performance of some particle air cleaners

Very limited data available on pollutant removal performance in buildings

Can produce ozone, see comments on ozone air cleaners

Quiet and energy efficient

Usual application is a standalone portable air cleaner

No direct measured data on how these devices affect health; however, ozone generating air cleaners can raise indoor ozone above levels known to be harmful to health

Plants

Plants in buildings can remove some volatile organic compounds

Quiet and energy efficient

Not proven to significantly reduce indoor pollutant levels with practical number of plants

Plants and molds on plants and soil can be a source of pollutants

Plants placed throughout building or in attached greenhouse

One system forces air through plant root zone

No direct measured health data