Humidity isn’t just a comfort metric it’s a force multiplier for air quality, according to Condair Australia managing director, Blake Phelps.
In a whitepaper on healthy buildings, Phelps said raising relative humidity (RH) to optimal levels (typically in the 40–60% range) can change how airborne particles behave.
He said fine particulates like PM2.5 (particles smaller than 2.5 microns) become heavier, clump together, settle faster, and are more readily trapped by filters.
“In dry air, small particles stay airborne longer. They remain suspended due to their tiny size and low mass, making them harder to capture and easier to inhale deep into the lungs,” Phelps said.
“This is especially true for PM2.5, a class of particles linked to respiratory disease, cardiovascular issues, and overall mortality.
“However, when humidity rises it creates hygroscopic growth: Many particles absorb moisture and grow in size.
“Filters perform better at capturing larger particles. In essence, controlling humidity doesn’t replace filtration, it supercharges it.”
Phelps said modern building design often emphasises air exchange rates and filtration while neglecting humidity control. This creates a missed opportunity.
Moreover, HVAC systems often actively dry the air during cooling cycles, pushing RH well below optimal levels.
“Without deliberate humidification, we’re handicapping our own investments in air cleaning technology,” Phelps said.
“Maintaining RH between 40% and 60% doesn’t just help filters, it reduces viruses and bacteria in the air and on surfaces.”
It also improves occupant comfort and protects building materials and furnishings from excessive dryness.
“By calming the air, making it less turbulent with fine, hard-to-capture particles, we create healthier, more comfortable indoor environments, often with reduced energy and maintenance costs over time,” Phelps said.
“Humidity control shouldn’t be an afterthought. It should be a deliberate part of an integrated air quality strategy.
“A properly designed HVAC system that actively manages humidity alongside filtration and ventilation delivers vastly superior outcomes.”