Polvo fino (PM2.5) en casa — qué saber y cómo reducirlo

PM2.5 — the "invisible dust" that actually matters

PM2.5 particles — particulate matter under 2.5 microns — are small enough to reach the lung alveoli and from there the bloodstream, and the WHO links them to cardiovascular and chronic respiratory disease and, with prolonged exposure, to documented excess mortality. They're the kind of pollutant that isn't visible to the naked eye and doesn't leave "dust on the furniture", so they often go unnoticed. The good news is that at home most of the sources are within your control, and the tools to manage them aren't expensive or complicated.

What PM2.5 is (and why it's different from "normal dust")

Particulate is classified by size: PM10 are particles up to 10 microns (pollen, household dust, coarse soot), PM2.5 are particles up to 2.5 microns (combustion, traffic, cooking), and PM1 are ultrafine particles up to 1 micron (smoke, exhaust fumes). The smaller they are, the deeper they penetrate the lungs — PM2.5 reaches the alveoli, PM1 enters the bloodstream.

The practical difference is that visible dust on furniture is almost always PM10 and above — annoying but less concerning for health. PM2.5 instead isn't visible and accumulates in the hours when you cook, light candles or leave the hood off. That's why the problem escapes daily observation: the floor looks clean, but the air we breathe in the hours after intense cooking can have particulate levels a hundred times higher than normal.

The indoor sources of PM2.5

Cooking, the main source

Cooking is by far the most important indoor source. Frying can push kitchen PM2.5 to 200–1000 µg/m³ temporarily; grilling gives similar values; burnt food produces 5–10 minute spikes that contaminate the whole home's air if the hood isn't on. The strategy has three components: the cooking hood always on during cooking (cuts PM2.5 by 60–80% if properly sized), opening the window straight after for 5–10 minutes, and where possible favouring steam or oven cooking over frying.

Candles, incense, smoke

Paraffin candles release PM2.5 and volatile organic compounds, incense releases far more PM2.5 than a candle, and in small rooms levels rise quickly. Cleaner alternatives are soy or beeswax candles and cold-diffusion essential oil diffusers (no combustion). On the cigarette-smoke front — and vaping, which many believe "clean" but produces particulate similarly — the answer is straight: don't smoke at home.

Vacuums without HEPA

Vacuums without a HEPA filter throw the finest particles back into the air through the filter or the exhaust, with the paradoxical effect that during and after vacuuming indoor PM2.5 rises rather than falls. The solution is a vacuum with a HEPA H13 or higher filter — the same recommendation as the mites and dust guide.

Fireplaces and wood stoves

Even modern fireplaces and wood stoves have non-trivial indoor PM2.5 emissions. To minimise them you need well-seasoned wood (humidity below 20%), optimal draw, and annual chimney maintenance.

Strategies to reduce indoor PM2.5

Targeted ventilation

The principle is simple: ventilate when outside air is better than inside air. The flat's windows aren't all equal, and neither are all hours of the day. Early morning (6–8) and late evening (after 22) are the hours with less traffic and therefore lower outside PM2.5. Rush hour (8–10 and 17–19) is less ideal for open windows. And on winter thermal inversion days (January–February in Ticino), checking UFAM's airpollution.ch is a habit that pays off: if outside PM2.5 is above 25 µg/m³, it's better to ventilate less and rely on an indoor purifier.

HEPA air purifiers

In a closed room — the bedroom we sleep in for eight hours, the living room we spend evenings in — a purifier with HEPA H13 or higher filter significantly reduces PM2.5. The key parameter is the CADR (Clean Air Delivery Rate), which measures how much clean air it produces: for a 25–30 m² room you need a CADR of at least 200 m³/h. The reliable brands — Philips Series 1000–3000, Dyson Pure, Levoit Core, Xiaomi Mi — sit between CHF 200 and CHF 600 depending on model, and filters need replacing every 6–12 months. It's the single investment with the best return for those who live in central Lugano or in high-traffic areas.

Optimising cooking and cleaning

Habits in the kitchen count as much as the equipment. The hood always on during cooking — a detail that many open-space kitchens leave off because of noise — is fundamental, as are hood filters washed or replaced regularly (clogged filters cut effectiveness by 50%) and lids on pots when possible to reduce vapours. On cleaning, weekly vacuuming with HEPA moves PM2.5 from floors to the filter rather than back into the air, and dusting with a barely-damp cloth captures particles instead of lifting them.

The Ticino-specific situation

In winter, the Sottoceneri (Lugano, Mendrisio) experiences a recurring meteorological phenomenon that makes PM2.5 more critical than elsewhere: the thermal inversion. Cold air stagnates in the basin, and pollutants stay trapped near the ground for three-to-seven consecutive days. UFAM data show Lugano-Pregassona an annual PM2.5 average of around 14–18 µg/m³ — below the European limits but well above the WHO limit of 5 µg/m³ — with winter peaks above 50 µg/m³ in prolonged episodes.

The strategy for the winter months combines regular consultation of airpollution.ch with limited ventilation on serious-inversion days and the use of an indoor purifier. Intense cooking with a broken hood or clogged filters is particularly to be avoided in these phases, because kitchen PM2.5 stacks on top of what filters in from outside.

When to measure and when to see a doctor

For those with asthma or COPD, young children with recurrent bronchitis, elderly people with cardiovascular issues, or who live in a home near a busy road, a PM2.5 indoor sensor is worth it. Home models (Awair, Atmotube, Xiaomi) cost CHF 80–200 and let you understand which household activities raise levels, know when to ventilate and when not, and verify the purifier's effectiveness over time.

Prolonged exposure to high PM2.5 is associated with chronic bronchitis, worsening of asthma, atherosclerosis in the long term and increased cardiovascular risk. Symptoms that warrant a medical check are persistent cough lasting more than three weeks, shortness of breath inside the home (that fades on going out), sore throat or headache associated with time spent at home, and unexplained chronic fatigue. When in doubt, talking to a family doctor is the first step.

What does NOT work against PM2.5

When to rely on a professional