As the fight to stem the impact of COVID-19 continues, without a viable vaccine in sight for the immediate future, social distancing and stringent personal hygiene remains the key advice from governments around the world in halting the spread of the virus. Whilst maintaining hand and surface hygiene is a sensible strategy for preventing spread through direct contact and short-range large droplet spray, to truly control disease outbreaks we must focus on the role of indoor air on disease transmission and occupant health.For example, a largely overlooked aspect of indoor air that contributes to both disease transmission and poor occupant health is dry air. In climates with cold winters, outdoor air is drawn into a building and heated to comfort temperatures. This drastically lowers the indoor relative humidity, creating a dangerous condition for people indoors, especially in this time of COVID-19 disease. When the indoor relative humidity is less than 40 per cent, human occupants are more vulnerable to viral respiratory infections and the SARS-CoV-2 virus is more plentiful and infectious in the inhaled air.