As winter approaches, the air across several Indian cities is likely to become harder to ignore. Smoggy mornings, hazy skies, and rising pollution levels often prompt families to rethink the air they breathe at home. Suddenly, an air purifier begins to look less like a luxury and more like a practical addition to the living room or bedroom.
But walk into a store or browse online, and you will find air purifiers promising everything from cleaner air to near-total particle removal. One term appears repeatedly: HEPA.
So, what does it actually mean? And how do you know whether the air purifier you are considering will do its job?
Here are five things worth checking before you bring one home.
1. First, understand what HEPA means
HEPA stands for High-Efficiency Particulate Air. In simple terms, it refers to a filter designed to trap tiny particles suspended in the air as it passes through the filter.
According to the US Environmental Protection Agency (EPA), a HEPA filter can theoretically remove at least 99.97% of airborne particles measuring 0.3 microns. To put that into perspective, a micron is one-millionth of a metre.
These particles can include fine dust, pollen, mould spores and smoke particles. This makes HEPA filtration particularly useful when outdoor pollution finds its way indoors or when household dust and allergens become a concern.
Choosing an air purifier with the right Clean Air Delivery Rate (CADR) can make a difference to how effectively it cleans the air in a room. Photograph: (Hindustan Times)
However, not every product that mentions HEPA necessarily meets the same standard. Terms such as “HEPA-type” and “HEPA-like” do not, by themselves, establish that a filter meets a recognised HEPA performance specification.
What to check: Look for a clearly stated filter grade and supporting performance information, rather than relying on the word HEPA alone.
2. Choose a purifier that suits your room
Imagine buying a powerful air purifier for your bedroom, only to find that it struggles to clean the air in your larger living room. The problem may not be the filter itself, but the amount of air the machine can process.
This is where CADR, or Clean Air Delivery Rate, comes in. It tells you how much filtered air a purifier delivers over a given period. A higher CADR generally means the machine can clean the air faster, provided the room size and other conditions are comparable.
A purifier with a highly efficient filter may still be less effective in a large room if its airflow is insufficient.
What to check: Match the manufacturer’s recommended room size and CADR to the space where you plan to use the purifier. A bedroom and an open-plan living area may need different capacities.
3. Remember that HEPA filters do not remove everything
HEPA filters are designed to capture particles, not every type of air pollutant. They do not, on their own, remove most gases, volatile organic compounds (VOCs) or odours.
For instance, cooking can release particles into the air, while certain paints, cleaning products and new furniture can release gaseous chemicals.
An activated-carbon filter can help adsorb some gases and odours. This is why some air purifiers combine HEPA filtration with activated carbon to tackle different kinds of indoor pollutants.
While HEPA filters capture airborne particles, activated-carbon filters help tackle certain gases, chemicals and household odours. Photograph: (Livemint)
What to check: If odours or gaseous pollutants are a concern, look for a purifier with an activated-carbon stage in addition to its particle filter. Check the manufacturer’s specifications for what it is designed to remove.
4. Check the cost and availability of replacement filters
Buying the machine is only the first expense. Filters collect particles over time and eventually need maintenance or replacement to keep the purifier working effectively.
Replacement intervals vary depending on the model, how often it runs and the pollution levels in your surroundings. A filter used through a heavily polluted winter may need attention sooner than one used in cleaner conditions.
What to check: Before purchasing, find out the price of a compatible replacement filter, whether it is readily available and how often the manufacturer recommends replacing it. Also check which parts can be cleaned and which must be replaced.
5. Look beyond the filter when comparing models
A good filter is important, but the machine around it matters, too. Noise levels can affect whether you are comfortable running it at night, while energy consumption can influence your electricity bill if you use it for several hours each day.
It is also worth checking the manufacturer’s safety information. Some air-cleaning technologies, particularly ozone-generating devices, can introduce pollutants rather than simply remove them.
Understanding how different filters work can help families make informed choices about improving indoor air quality. Photograph: (MarketWatch)
What to check: Compare noise levels, power consumption, warranty, service support and safety specifications. Choose a model you can comfortably run and maintain as recommended.
Cleaner air starts with informed choices
As pollution levels rise, wanting to make the air at home a little cleaner is understandable. For families, it could mean being more mindful of the air children play in, the bedrooms where everyone sleeps, and the spaces where they spend most of their day.
An air purifier can be one part of that effort. Taking a little time to understand the filter, choose the right model and maintain it well can help you make a more informed choice for your home. After all, cleaner indoor air begins with knowing what you are bringing through the door.
