Before You Buy: Why This Checklist Exists
You've decided you need an air purifier. Maybe the AQI crossed 300 last week, a doctor recommended one, or you've just moved into a new flat next to a construction site. Whatever the reason, you're now staring at Amazon listings ranging from ₹6,000 to ₹80,000, and the specs mean nothing to you.
You're not alone. Most Indian buyers pick an air purifier based on the brand name, the number of stars, or whichever model is on a sale that day. Three months later, they're wondering why the air in their bedroom still smells like Delhi in November.
This checklist exists to prevent that. Run through each of these 8 checks before you buy, and you'll walk away with a purifier that actually works for your room, your city, and your budget.
Is the CADR Right for Your Room?
CADR, Clean Air Delivery Rate, is the single most important number on any air purifier's spec sheet. It tells you how many cubic metres of clean air the purifier delivers per hour. The higher the CADR, the faster it cleans your room.
Not sure what CADR you need for your room? Use our Air Purifier CADR Calculator to find the right size in under a minute.
The rule of thumb: Your purifier should achieve at least 5 air changes per hour (ACH) in your room. That means it should clean the entire volume of air in your room at least five times every hour. During high-pollution events such as Delhi smog season, construction nearby, and Diwali, aim for 6–8 ACH.
| Room Type | Typical Size | Minimum CADR Needed |
|---|---|---|
| Small bedroom | 100–150 sq ft | 150–220 m³/h |
| Standard bedroom | 150–250 sq ft | 220–350 m³/h |
| Living room / hall | 300–500 sq ft | 400–600 m³/h |
| Large open-plan space | 500+ sq ft | 600+ m³/h |
Assuming a standard 10-foot ceiling height.
The Indian context matters
Most air purifier brands rate their CADR based on an 8-foot ceiling, standard in Western homes. Indian apartments, particularly in newer buildings, often have 9–10 foot ceilings. This means the actual air volume in your room is 12–25% more than the brand's coverage area suggests. If your room has high ceilings, upsize accordingly.
Also, if you live in Delhi-NCR, Mumbai, or any city where winter AQI regularly crosses 200–300, add a 20–30% buffer to your CADR requirement. You want a purifier that handles your worst-air days at medium fan speed, not one that's maxed out and noisy even on a moderate pollution day.
Is It a True HEPA Filter, and What Grade?
"HEPA" is the most misused word in the air purifier market. Every brand claims it, but not all HEPA filters are equal. Before you buy, check which grade of HEPA the purifier actually uses.
Captures 99.97% of particles at 0.3 microns. This is the minimum you should accept for Indian urban conditions. It handles PM2.5, dust, pollen, smoke, and most allergens.
Captures 99.995% of particles at 0.1 microns. Worth it if someone in your home has severe asthma, COPD, or a compromised immune system, or if you're dealing with heavy vehicular pollution infiltration.
Watch out for "HEPA-type" or "HEPA-like" filters. These are marketing terms with no standardised testing behind them. They may capture only 85–90% of particles, which sounds good until you realise it means 10–15% of fine particles pass straight through. In a city with PM2.5 levels of 150–200 µg/m³, that's a significant amount of pollution still circulating in your home.
Does It Have an Activated Carbon Filter, and How Much?
A HEPA filter handles particles. It does nothing for gases, odours, or volatile organic compounds (VOCs). For that, you need activated carbon. This matters more than most buyers realise. Indian homes face a specific cocktail of gaseous pollutants:
- •VOCs from fresh paint, new furniture, flooring adhesives, and cleaning products
- •Cooking fumes, especially if you cook with gas, which produces nitrogen dioxide (NO₂)
- •Vehicle exhaust infiltration, petrol and diesel emissions contain benzene, toluene, and other harmful gases that HEPA does not touch
- •Construction dust odours, nearby demolition and fresh concrete release chemical off-gassing
The problem is that activated carbon filters vary enormously by weight and quality. A purifier with 50 grams of carbon will exhaust within a few weeks in a polluted Indian home. A purifier with 500+ grams will last a year or more.
Carbon filter weight by price tier
- Budget (under ₹10,000): Token carbon layers of 30–80 grams, enough for light odour control.
- Mid-range (₹15,000–₹30,000): Often 150–300 grams, adequate for most Indian homes.
- Premium (₹30,000+): Substantially more carbon, with some models exceeding 500 grams.
If you live near a busy road, an industrial area, or a construction site, or if someone in your home cooks extensively with gas, prioritise carbon filter weight, not just presence.
What Is the Annual Filter Cost?
This is the check most buyers skip entirely, and it's the one that causes the most regret. An air purifier is not a one-time purchase. It's an appliance with recurring costs. HEPA and carbon filters need replacement every 6–12 months depending on usage and pollution levels. If you run the purifier 10–12 hours a day in a polluted Indian city, filter life is on the lower end of that range.
3-Year Total Cost of Ownership: An Example
Purifier A
Purchase: ₹12,000
Filters: ₹3,500/year × 3 = ₹10,500
Total: ₹22,500
Purifier B
Purchase: ₹18,000
Filters: ₹1,800/year × 3 = ₹5,400
Total: ₹23,400
They're essentially identical in total cost, but the cheaper-looking option isn't actually cheaper.
The premium brand trap: Some premium brands price replacement filters very aggressively. Always calculate the total 3-year cost of ownership, not just the sticker price.
What Is the Noise Level at Your Typical Fan Speed?
An air purifier you turn off because it disturbs your sleep is worse than useless. Noise is consistently one of the top reasons Indian buyers are dissatisfied with their purchase, and it's almost never mentioned in marketing materials.
| Noise Level | What It Sounds Like | Usable For |
|---|---|---|
| Below 25 dB | Near-silent, rustling leaves | Bedroom overnight |
| 25–35 dB | Quiet library | Bedroom, study, baby's room |
| 35–45 dB | Quiet conversation | Living room background |
| 45–55 dB | Normal conversation | Only tolerable on low fan setting |
| Above 55 dB | Loud fan | Avoid for any occupied room |
The complication
Brands quote their lowest possible noise level, which is typically at the minimum fan speed. At maximum fan speed, which is when you actually need the purifier most (during high-pollution events), the same model may produce 55–65 dB. That's loud enough to disrupt sleep and conversation. Check the noise level at medium fan speed, not minimum. If a brand only publishes the minimum fan noise, treat that as a red flag.
Does It Have a Reliable Auto Mode and Air Quality Sensor?
The best air purifier strategy for Indian homes is to run it continuously on auto mode, letting it adjust its own fan speed based on real-time air quality. This saves energy, extends filter life, and gives you visible feedback on your indoor air quality.
For auto mode to work well, the built-in air quality sensor needs to be accurate. Unfortunately, the sensors in budget purifiers are often extremely basic: they detect large visible particles but miss the fine PM2.5 and PM10 that are most harmful.
What to look for in a sensor
- •PM2.5 laser sensor (not just a simple dust sensor)
- •Numerical AQI display (not just a colour indicator)
- •VOC detection is a bonus for Indian homes with cooking or new furniture
Placement matters: Even a good purifier sensor is measuring the air inside the purifier, not the centre of your room. Keep the purifier away from walls, not hidden in corners, and not near sources of direct particle input like a cooking range. The purifier's intake and output geometry also shapes how well the sensor reads the room. Mid-range and premium purifiers now include reasonably accurate PM2.5 sensors. Budget models under ₹8,000 typically have basic sensors that don't justify the "auto mode" label.
Avoid Ozone-Generating Technologies for Daily Use
This is a safety check, not a performance check. Some air purifiers use ionisers, plasma generators, UV-C lights, or ozone-based purification. The marketing language is compelling, "kills bacteria", "destroys viruses", "ionises the air". What this marketing rarely mentions is that these technologies can generate ozone as a byproduct.
Ozone (O₃) is a respiratory irritant. It can cause throat irritation, coughing, and worsening of asthma symptoms: exactly the opposite of what you bought the purifier for. The WHO and US EPA have both flagged ozone-generating air cleaners as a health concern in enclosed spaces.
What to look for
| What to Look For | Details |
|---|---|
| Check for "ozone-free" or "zero ozone emission" certification | Always verify this on the spec sheet before purchasing. |
| Ioniser with a physical on/off switch | So you can disable it when not needed. |
| Prefer mechanical HEPA + carbon filtration | No plasma, no UV, no ioniser needed for effective home air cleaning in India. |
Is the Brand Reliable for After-Sales Service in Your City?
The final check is practical, not technical, but it's what separates a purifier that lasts 5 years from one that becomes an expensive piece of furniture after the first filter change.
Ask these questions before buying
| Question | Why It Matters |
|---|---|
| Is there a service centre in my city? | International premium brands have good service networks in metros. In tier-2 cities, some brands have very limited or no service presence. |
| Will the brand continue selling replacement filters for this model? | A purifier is only useful as long as you can buy filters for it. Smaller brands and white-label Chinese imports are at risk of discontinuing model lines within 2–3 years. |
| Does the brand honour its warranty in India? | Read the warranty terms carefully. Some brands imported through grey channels come with international warranties that are not valid in India. |
Ready to Find the Right Purifier?
Now that you know what to check, use our tools to find a purifier that fits your room, your city, and your budget. See this checklist applied to the Xiaomi AP4 vs AP4 Lite and the Dyson HushJet HJ10, or read our walkthrough of the comparison engine.
Email us at indoorairguide@outlook.com