People living in cities hundreds or thousands of kilometers away from the fire fronts are exposed to the same smoke that blankets the Cerrado, the Amazon, and the Pantanal during the driest months. In 2024, according to INPE, Brazil recorded more than 80 thousand fire hotspots in September alone, with documented clouds of soot crossing the Southeast and leading to events such as the “dark rain” recorded in Porto Alegre. The air pollution generated by the fires is not confined to the area where the fires originated.
How smoke moves
The particles generated by the combustion of dry vegetation, especially the fine particulate matter known as PM 2.5, are light enough to remain suspended for long periods and travel extensive distances through the atmosphere. Studies by MapBiomas and IPAM have shown that, in 2024, smoke concentrated in the Amazon reached the Midwest, Southeast, and South, compromising air quality in capital cities far from the fire hotspots. During periods of prolonged drought, dry soil and parched vegetation exacerbate the spread of fires and increase the amount of pollutants released.
For those outside the fire zone, the problem comes through the atmosphere. Particles enter indoor environments through openings, cracks, poorly sealed ventilation systems, and outdoor air intakes on HVAC equipment.
Why Indoor Environments Are Not Automatically Safe
There is a common misconception that closing doors and windows solves the problem. The reality is more complex. In buildings with high levels of natural air infiltration, poor sealing, or air conditioning systems that draw in untreated outside air, indoor air quality follows the deterioration of outdoor air with a slight delay. In corporate and residential environments with low air exchange rates, the problem takes on a different nature: CO₂ accumulates, fatigue sets in, and the air becomes uncomfortable.
The balance between sealing and ventilation is the key technical issue. Sealing everything off reduces smoke ingress but worsens indoor air quality for other reasons. Ventilating without filtration brings outdoor problems indoors. The solution lies in ventilating with proper filtration.
What to Consider in Residential Settings
In homes, equipment such as air purifiers with HEPA filtration reduce the concentration of particulate matter in the environment. When choosing a model, it is important to consider the treated airflow rate in relation to the room’s volume. Small units installed in large rooms have limited effectiveness. Split-system units with supplemental filtration help, but they do not replace a suitable air purifier when the goal is to control fine particulate matter.
Patrick Galletti, an HVAC engineer and CEO of Grupo RETEC, points out that during periods of heavy smoke, the technical recommendation involves three approaches: reducing exposure to outdoor air during the most critical times, staying hydrated, and using air purification or HVAC equipment with adequate filtration in environments where people spend the most time.
What to Consider in Corporate Construction Projects and High-Occupancy Environments
In commercial buildings, hospitals, schools, and logistics centers, the solution lies in the HVAC and ventilation design. Systems that combine air handling units with F7, F9, or HEPA filtration, motorized dampers at outdoor air intakes, and air quality sensors allow for regulating the amount of outside air that enters during critical weather events. In hospitals, this technical system is already part of daily operations. In offices and corporate environments, it has gained prominence in recent years.
The correct selection of components depends on the thermal load, occupancy, space usage, and regulatory requirements. High-efficiency filters in improperly sized systems lose performance. High air change rates in environments without adequate filtration only exacerbate the problem.
Practical checks for the wildfire season
- - Check the status and class of the HVAC system's filters.
- - Check the sealing of windows, doors, and ducts in sensitive areas.
- - Evaluate the placement of outdoor air intakes in relation to sources of pollution.
- - In high-occupancy areas, monitor CO₂ and PM 2.5 levels using sensors.
- - Verify compliance with the PMOC and the frequency of preventive maintenance.
RETEC provides solutions for air conditioning, ventilation, exhaust, and air treatment in medium- and large-scale projects. For technical specifications tailored to your application, please contact the sales team.
We participated in a feature on this topic in Casa e Jardim (Editora Globo). The risks of wildfires for those far from the fire sites were discussed in a feature featuring Patrick Galletti, CEO of Grupo RETEC. Read more at: https://revistacasaejardim.globo.com/comportamento/bem-estar-e-saude/noticia/2024/09/queimadas-os-perigos-mesmo-para-quem-esta-longe-de-focos-e-como-se-proteger.ghtml