Air Quality · Wildfire & Smoke
When wildfire smoke or fire damage fills the air, the right filtration protects health and clears the space. But smoke is two problems in one — tiny particles and gases — and beating it takes the right combination of HEPA and activated-carbon filtration. Here's what works, why, and how to size the equipment you need.
Smoke isn't a single thing. It's a mix of two very different hazards, and each needs a different kind of filter:
1. Fine particulate (PM2.5). Wildfire and fire-damage smoke is full of microscopic soot and ash particles — many 2.5 microns or smaller. These are small enough to bypass your body's defenses and lodge deep in the lungs, which is why smoke events trigger health warnings for sensitive groups. You can often see this as haze; you can't filter it with an ordinary furnace filter.
2. Gases, VOCs and odor. Smoke also carries volatile organic compounds (VOCs), combustion gases and the acrid smell that lingers long after a fire. These are molecules, not particles — and this is the part most people get wrong: a HEPA filter does not capture them.
A true HEPA filter removes 99.97% of airborne particles 0.3 microns and larger — the exact range that includes the fine PM2.5 in smoke. Running air through a HEPA air scrubber pulls soot, ash and fine particulate out of the space continuously. For the visible haze and the lung-damaging particles, HEPA is the answer.
Key limitation: HEPA filters capture particles — they do not remove gases, VOCs or smoke odor. For those you need a second stage.
Activated carbon (charcoal) filters work by adsorption — the gas molecules and VOCs stick to the enormous internal surface area of the carbon. This is what removes the smell of smoke and the invisible combustion gases that HEPA passes straight through. For any smoke or fire-odor situation, a carbon/VOC stage is what actually clears the air of that lingering burnt smell.
An air scrubber is a powerful, portable filtration unit that pulls large volumes of air through its HEPA (and carbon) stages and returns clean air to the room — over and over. Sized correctly, it cycles the entire volume of air in a space several times per hour (measured as air changes per hour). That continuous turnover is what actually clears a smoky space, versus a small consumer purifier that can't keep up with the volume. Air scrubbers can also create negative pressure to keep smoke or contaminants contained to one area.
Smoky conditions call for higher air turnover than routine dust. Enter your room size and how heavy the smoke is to estimate the HEPA scrubbers you need — then reserve them from our rental store.
Allied Rental Company stocks HEPA air scrubbers and negative-air machines with carbon-filter options — delivered across the San Francisco Bay Area, available 24/7 during smoke and fire events.