Since the 1970s, homes in North America have increasingly been designed with more energy-efficient and airtight windows, doors, insulation, and building envelopes. The advantage of this design is that it reduces the loss of heated or cooled air, thereby conserving energy. The downside is that tightly sealed homes can have poor indoor air quality if there is insufficient ventilation.

Gases and particles suspended in the air are major factors contributing to poor indoor air quality. Common household sources include cooking fumes, paint, wooden furniture, household cleaning products, beauty products, humidifiers, and combustion from heating or cooking appliances. Dust, pollen, and other particles can also be brought indoors on the clothes and shoes of family members returning home. Without adequate ventilation, filtration, and source control, some indoor pollutants can accumulate and may contribute to irritation, allergies, or respiratory problems.

By Michael Chiu, MWS, CI
Previously published in Ming Pao Daily News – Updated and Revised in 2026