When the sky turns grey: Simple ways to stay safe from bushfire smoke

Words: Claire Bird

Sunday 7 September marked the UN International Day of Clean Air for Blue Skies, a reminder that the quality of the air we breathe is as important to our health as the food and water we consume. It pictures a cloudless sky that no longer looks blue, which can mean the air is polluted.

Air pollution worsens the impact of all fatal diseases. It not only increases risks around asthma, COPD and lung cancer, but also raises rates of heart disease and stroke. The main culprits are tiny, completely invisible yet highly dangerous airborne particles. Particles small enough to reach deep into our lungs are called PM_2.5. Even smaller PM₁ particles cross into the bloodstream, reaching all the organs of the body, where they may cause harm.

One of the most potent sources of these particles is bushfires. Smoke easily enters homes and workplaces through windows, vents or even small gaps in walls.

The three actions that matter most during bushfires are:

1. Keep smoke out. Airtight building design helps. In existing buildings, closing windows, sealing cracks and shutting off outdoor air dampers can make a big difference. Short-term increases in indoor carbon dioxide (CO₂) when closing the building as much as possible are usually manageable at levels up to 1500 parts per million (ppm) without impact on health or comfort. Workplace limits are 5000 ppm over an eight-hour workday for CO₂ and the World Health Organization recommends indoor limits of 15 µg/m³ for PM_2.5 over a 24-hour period. Monitoring CO₂ and PM_2.5 during a bushfire can help balance fresh air with bushfire safety.
2. Clean the air. Portable HEPA filters are the best way to cut PM_2.5 levels indoors. Other technologies are evolving for bushfire smoke and odour mitigation in HVAC systems. 
3. Clean the building. Smoke leaves behind more than just ash. Plastics, furniture, paints or wiring release toxic chemicals during a fire from neighbouring properties or surrounding infrastructure that settle in HVAC systems and on surfaces. Cleaning properly means using the right methods, testing to confirm safety and engaging qualified cleaning professionals. The ANSI/IICRC S700 outlines best practices for fire and smoke restoration, while the ASHRAE Guideline 44 assists in protecting building occupants from wildfire smoke.

We may not be able to stop bushfires, especially as the climate changes. But we can take practical steps to protect our homes and workplaces during the fire and after the smoke clears. That is progress we can make right now.