Large parts of North India, including the national capital region of Delhi, are currently engulfed in a severe and hazardous pollution crisis. Air Quality Index (AQI) levels have consistently breached the 'severe' and 'hazardous' categories, making clean air a scarce commodity. While relocating is not a feasible option for most residents, air purifiers have become an essential line of defence for indoor spaces.
Contrary to popular belief, indoor air is often as toxic, if not more, than outdoor air due to trapped dust, pollen, smoke, and germs. This reality has transformed air purifiers from a luxury item into an absolute necessity for health. Dr. Anshuman Kaushal, MD, recently took to Instagram to demystify the process of choosing an effective air purifier, moving beyond marketing gimmicks like fancy displays or remote controls.
The Four Pillars of an Effective Air Purifier
Dr. Kaushal emphasises that a good air purifier hinges on four critical technical and practical aspects. Ignoring these, he warns, can lead to wasted money and continued exposure to dirty air, while a well-chosen device can significantly reduce allergies, asthma attacks, and sick days.
1. Understanding CADR: The Cleaning Speed
CADR, or Clean Air Delivery Rate, is the most important metric for an air purifier's performance. It measures how quickly the device can remove smoke, dust, and pollen from the air, expressed in cubic feet per minute (CFM). A higher CADR number indicates faster cleaning. For instance, a unit with a 300 CADR can refresh the air in a room four to five times every hour.
Dr. Kaushal cautions that a low CADR will leave pollutants lingering. He advises consumers to look for the AHAM (Association of Home Appliance Manufacturers) verification seal, which provides real, tested numbers, and to avoid cheap models that advertise fake high CADR with weak filters. The CADR must be matched to your room size: 100-150 for small spaces and 300 or above for larger rooms.
2. The Non-Negotiable: True HEPA Rating
The filter is the heart of the purifier. A genuine True HEPA filter is certified to trap 99.97% of particles as small as 0.3 microns, which includes fine dust, pollen, and even virus particles. Dr. Kaushal strongly advises skipping 'HEPA-type' or 'HEPA-like' filters, as they are far less effective.
When paired with a high CADR, a True HEPA filter can remove 99% of allergens rapidly. Many models include an activated carbon layer to control odours. For sustained efficiency, filters should be replaced annually. Studies indicate that True HEPA filters can reduce asthma symptoms by 30-50%.
3. Matching the Purifier to Your Room Size
An incorrectly sized purifier is a common mistake. Your room's square footage directly determines whether the device will work effectively. Dr. Kaushal provides a simple formula: multiply your room's area in square feet by 2 to 4 to get the required CADR. For example, a 200 sq ft bedroom needs a purifier with a CADR between 400 and 800.
Always check the manufacturer's room size chart, which is typically calculated for standard 8-foot ceilings. Rooms with open layouts or high ceilings require a more powerful unit. Choosing the wrong size leads to wasted energy and money. Models with built-in air quality sensors can help verify performance.
4. Prioritising Night-Time Noise Levels
For bedroom use, quiet operation is paramount. Dr. Kaushal recommends selecting units that operate below 30 decibels (dB) on their lowest setting for whisper-quiet sleep. High-speed fans can exceed 50 dB, comparable to a loud conversation, which disrupts sleep.
Look for a dedicated 'sleep mode' that minimises noise. It's wise to check user reviews for real-world noise feedback, not just manufacturer claims. An 'auto mode' is beneficial as it adjusts the fan speed based on real-time air quality, staying silent when the air is clean. Noisy purifiers often get switched off at night, leaving the air unfiltered for hours, which studies link to worsened health outcomes.
Additional Expert Tips for Cleaner Indoor Air
Dr. Kaushal also suggests looking for the ENERGY STAR label for energy efficiency. Features like auto sensors and companion apps can help track air quality trends. Crucially, avoid purifiers that generate ozone, as it is harmful to lungs.
Consider the long-term cost per clean air: a unit with a high CADR may save on filter changes over time. Anecdotal evidence suggests families using effective purifiers report fewer respiratory issues and better concentration. For optimal performance, place the unit away from walls and corners to maximise airflow, clean the pre-filter monthly, and replace the main filter every 6 to 12 months.
