Wildfire Smoke: What Actually Protects Your Lungs

An increasingly common exposure with a narrow set of genuinely effective countermeasures.

Why wildfire smoke is worse than general pollution

Wildfire smoke is dominated by fine particulate matter, with PM2.5 concentrations during significant events reaching many times typical urban levels — occasionally into ranges classed as hazardous.

It also contains carbon monoxide, nitrogen oxides, volatile organic compounds including formaldehyde and benzene, and polycyclic aromatic hydrocarbons.

Where fires burn structures rather than only vegetation, the mixture additionally includes combustion products from plastics, treated timber, insulation and household chemicals, which is a materially different and more toxic exposure.

The particles are small enough to reach the alveoli, and ultrafine fractions can cross into the bloodstream, which is why wildfire smoke exposure has cardiovascular as well as respiratory effects.

What works

Stay indoors with windows and doors closed. The single most effective measure. Indoor PM2.5 during smoke events is typically a fraction of outdoor levels in a reasonably sealed building.

HEPA air filtration. True HEPA filters capture the relevant particle sizes effectively. Portable units sized for the room, run continuously, measurably reduce indoor concentrations.

Create one clean air room. Rather than trying to filter a whole house, choose one room — ideally a bedroom — seal it as well as practical, and run filtration there. This concentrates limited resources where they do most good.

Set HVAC to recirculate, not to draw in outside air, and upgrade to a high-MERV filter if the system tolerates it.

A properly fitted N95 or FFP2 respirator if you must go outdoors. Fit is everything — a respirator leaking around the edges provides a fraction of its rated protection. Facial hair at the seal substantially compromises it.

Recirculate in the car and use the cabin air filter setting.

Reduce physical exertion. Exercise multiplies ventilation and therefore the inhaled dose. Postpone outdoor training.

What does not work

• Cloth masks. Do not filter PM2.5 meaningfully.
• Surgical masks. Better than cloth for droplets, still inadequate for fine particulate, and they fit loosely.
• Bandanas or wet cloths. No meaningful filtration; a wet cloth may make breathing harder without filtering.
• Ozone generators and ionisers. Ozone is itself a respiratory irritant. Actively counterproductive.
• Houseplants. No meaningful effect at realistic densities.
• Air fresheners. Mask odour while adding VOCs.

Who is at higher risk

• People with asthma, COPD or other chronic respiratory disease.
• People with cardiovascular disease — smoke exposure is associated with increased cardiac events.
• Children, who breathe more air per kilogram of body weight and have developing lungs.
• Older adults.
• Pregnant women.
• Outdoor workers, who have the highest exposures and often the least control over them.

When to seek medical attention

Difficulty breathing that is severe or does not improve indoors. Chest pain or pressure. Wheezing that does not respond to your usual reliever. Persistent cough with fever. Dizziness or confusion. Palpitations.

Anyone with asthma or COPD should ensure they have adequate medication before smoke season and should have a clear action plan agreed with their doctor. Smoke events reliably increase exacerbations and emergency presentations.

After the smoke clears

Symptoms can persist for days to weeks after air quality normalises, reflecting the time airway inflammation takes to settle.

Ventilate thoroughly once outdoor air is genuinely clean, clean surfaces where ash has settled using wet methods rather than dry sweeping, and replace air filters, which will be loaded.