Healthy House, Victoria, Australia. Healthy House design

Frequently Asked Questions (FAQs)

11. Does filtration improve indoor air quality?

The use of ventilation to improve indoor air quality is the main approach taken for reducing the harmful effects of airborne pollutants that enter the home or are generated internally within the home.

Ventilation helps to remove and dilute airborne pollutants within the home but may actually increase such pollutants depending on external local environmental conditions.

Filtration can be used in conjunction with ventilation systems to further reduce airborne pollutants and thereby improve indoor air quality. Effective filtration relies on:

a filter that removes airborne pollutants such as particles and gaseous pollutants,
an appropriate rate of air flow through the filter, and
a ventilation system to ensure adequate air exchange throughout the home.

Filters are rated to ASHRAE Standard 52-76 American Society of Heating, Refrigerating, and Air Conditioning Engineers. However the efficiency of such filters is influenced by the rate of air that flows through them. Testing in-duct systems for "medium efficiency" has been undertaken by the U.S. Environmental Protection Agency and the results are shown below.

Exhibit 1. Filter Applications for In-duct Systems Based on ASHRAE Atmospheric Dust Spot Test
Air Cleaner Efficiency Ratings
10%	20%	40%	60%	80%	90%
Used in window air conditioners and heating systems Useful on lint. Somewhat useful on ragweed pollen. Not very useful on smoke and staining particles.	Used in air conditioners, domestic heating, and central air systems. Fairly useful on ragweed pollen. Not very useful on smoke and staining particles.	Used in heating and air conditioning systems, and as pre-filters to high efficiency cleaners. Useful on finer airborne dust and pollen. Reduce smudge and stain materially. Slightly useful on non-tobacco smoke particles. Not very useful on tobacco smoke particles.	Use same as 40%, but better protection. Useful on all pollens, the majority of particles causing smudge and stain, and coal and oil smoke particles. Partially useful on tobacco smoke particles.	Generally used in hospitals and controlled areas. Very useful on particles causing smudge and stain, and coal and oil smoke particles. Quite useful on tobacco smoke particles.	Use same as 80%, but better protection. Excellent protection against all smoke particles.
1. Efficiency rating by ASHRAE Standard 52-76 atmospheric dust spot test. Source: U.S. Environmental Protection Agency