Air Purifiers in Portugal: How to Choose the Best (HEPA, CADR, and Activated Carbon)

Air Purifiers in Portugal: How to Choose the Best (HEPA, CADR, and Activated Carbon)

An air purifier (also called an “air cleaner”) can help reduce particles such as fine dust (PM2.5), pollen, and indoor dust—especially when it’s a “mechanical” model with a HEPA filter and sufficient airflow. Evidence shows modest health improvements when used consistently, and HEPA is often the most effective option for particles.

Important: air purifiers do not replace ventilation nor do they solve all pollutant problems (e.g., gases/odors require specific filters).

1) What an air purifier actually does (and what it doesn't do)

Filters particles (the “main”)

  • Fine dust (including PM2.5), pollen, household dust, some aerosols

  • Useful for allergy sufferers, homes with pets, areas with traffic, smoke, and dusty seasons.

For particulate matter, the EPA recommends choosing equipment with a CADR appropriate to the room size and notes that many purifiers achieve high CADR using HEPA filters .

For odors and gases (VOCs), you need "charcoal".

The EPA states that for gases, you should look for an activated carbon filter (and that there isn't a classification system as widely used as CADR, which is for particulate matter).

Does it kill viruses?

DECO explains that a purifier does not "kill" viruses , although it may capture some particles/aerosols depending on the filter — but it does not "completely" protect against infections.

2) Why this matters in Portugal (PM2.5 and health)

The WHO recommends ambitious targets for PM2.5 (e.g., annual average of 5 µg/m³ ) and emphasizes that health effects occur even at low levels.
The European Environment Agency describes air pollution as one of the biggest environmental health risks in Europe.

There is evidence that HEPA air purifiers can reduce PM2.5 indoors , but factors such as ventilating with open windows can significantly reduce their effectiveness.

3) Filters: what to look for (without falling for marketing)

Pre-filter (required)

Catches large hairs/dust → prolongs the life of HEPA.

HEPA (for particles)

If the goal is allergies/PM2.5, prioritize HEPA. The classification and testing of HEPA/ULPA filters in Europe are framed by standards such as EN 1822 (basis for testing and classes).

Activated carbon (for odors and gases)

The more carbon material there is , the better the gas/odor control tends to be (the EPA mentions that it can be effective when there is enough material).

4) CADR and division size: the rule that decides everything

CADR is the most practical measure for comparing air purifiers (for particulate matter): it indicates the "volume of clean air" delivered. AHAM describes CADR and states that higher values ​​filter faster (dust, pollen, smoke).
The EPA emphasizes that you should choose a CADR that is "large enough" for the area where you will be using it.

How to calculate quickly (without complicating things)

  1. Calculate the volume of the division: m² × height (m) = m³

  2. Typical target: 4–5 renewals/hour (ACH) for home use.

  3. Recommended flow rate (m³/h): volume × 4 or × 5

Example: room 12 m², height 2.5 m → 30 m³
30 × 5 = 150 m³/h (CADR demand ~150 m³/h or higher)

5) Noise, fuel consumption and maintenance (where many people go wrong)

  • Noise: For bedroom use, check dB in "sleep" mode and at medium power (where you will actually use it).

  • Consumption: If you're going to work long hours, the automatic mode helps, but it also confirms the average consumption.

  • Filters: consider the annual cost (HEPA + carbon). A washable pre-filter is advantageous.

6) What to avoid: “ozone/ionizers” as a miracle cure

The EPA warns that ozone generators sold as "air cleaners" are not effective against several pollutants and can create problems (in addition to slow/ineffective reactions for many chemicals).
Rule of thumb: for home use, you prefer mechanical purification (HEPA + carbon) instead of "ozone".

7) How to use it to get results (and not frustration)

  • Place it where air circulates (not hidden behind furniture).

  • Keep doors closed whenever possible (purify “that” room).

  • It spends more time in medium power mode than in "turbo 10 minutes".

  • If the outside air is poor, opening windows can reduce the effect of HEPA.

FAQ

Does an air purifier help with allergies?
It can help reduce particles like pollen/dust when you have adequate HEPA and CADR.

Does it remove cooking and tobacco odors?
For odors/gases you need activated carbon ; CADR is for particles.

Does purifier “kill viruses”?
It doesn't "kill" viruses; it can capture some particles/aerosols depending on the system, but it doesn't provide complete protection.