How To Check Air Quality At Home India

Why Outdoor AQI Isn’t Your Answer

Almost everyone checking air quality opens an app showing a city AQI figure. Useful for
deciding whether to go running. Close to useless for deciding anything about your home.

That number comes from a monitoring station somewhere in the city, and it describes outdoor
air at that location. Your bedroom differs from it in both directions:

• Better, if the room is sealed and filtered — indoor levels can sit well
  below outdoor.
• Worse, if you are cooking, burning incense or a mosquito coil, or have
  just finished a renovation. Indoor sources can push a single room far above the city
  figure.

What a Home Monitor Measures

Most consumer devices report some subset of these:

Reading	What it tells you	Worth having?
PM2.5	Fine particulate — the main pollutant of concern	Yes. This is the number
PM10	Coarser dust	Useful, secondary
CO2	Ventilation adequacy — rises in a closed occupied room	Genuinely useful, and often missing
VOC / TVOC	Gases from paint, furniture, cleaning products	Indicative only — most sensors are not specific
Temperature and humidity	Comfort, and mould/dust-mite risk above ~60% RH	Useful context

If a device measures only one thing, PM2.5 is the one to have. If it measures two, PM2.5 and
CO2 together cover the two genuinely distinct problems: what is in the air, and
whether the room is ventilated. A purifier addresses the first and does nothing
for the second.

How Accurate Are Cheap Monitors?

Worth being straightforward about this, because both the marketing and the backlash overstate
their case.

Consumer monitors almost all use laser light-scattering: air is drawn past a
laser, particles scatter the light, and the device infers particle count and estimates mass. It
is an inference, not a direct measurement. Reference-grade instruments used at regulatory
stations work differently and cost orders of magnitude more.

Practical consequences:

• Absolute values can be off, sometimes substantially, and they drift with
  humidity — high humidity tends to inflate readings.
• Relative changes are reliable. If it reads 40 and jumps to 180 when you
  start frying, that jump is real even if neither figure is exact.
• Consistency beats accuracy for household use. The same device in the same
  place, watched over time, tells you what you need.

Reading the Numbers

India’s AQI bands — Good, Satisfactory, Moderate, Poor, Very Poor, Severe — are designed for
outdoor reporting. Applied indoors they are a reasonable rough guide, with two caveats worth
holding on to.

First, lower is always better. There is no threshold below which fine
particulate becomes harmless; WHO guideline values are considerably stricter than most national
standards, including India’s.

Second, compare against outdoors rather than against an ideal. Most Indian
homes will not achieve single-digit PM2.5. A realistic and genuinely valuable goal is a bedroom
running well below the outdoor figure during the bad months — and knowing that it is.

Checking Without Buying Anything

Two free diagnostics that tell you a surprising amount:

The window-sill test. Wipe a road-facing sill completely clean and note the
date. Wipe an interior surface far from any window equally clean. Compare after a week. If the
sill is dramatically dirtier — especially with black deposit — outdoor infiltration dominates,
and sealing matters more than filtering.

The return test. Leave the house for a few hours and pay attention to the
first breath on returning. You acclimatise to your own home’s air within minutes, so that first
impression — musty, smoky, stale — is the most honest reading you will get without a device.

Using It to Actually Change Something

A monitor that produces numbers nobody acts on is an expensive ornament. The value is in
running specific tests, once:

1. Baseline. Leave it in the bedroom for two days. Note the overnight
   pattern.
2. Cooking test. Watch it through a full cooking session with the extractor
   off, then repeat with it on. Most people find this the most persuasive thing the device ever
   does.
3. Sealing test. Read the bedroom before and after weather-stripping the
   window. This tells you whether infiltration is your problem.
4. Purifier test. Closed room, purifier on, watch how long it takes to fall
   and how far. If it barely moves, the unit is undersized or the filter is spent.
5. Filter check. Repeat the purifier test every couple of months. When
   clearing takes noticeably longer than it used to, the filter is done — regardless of what the
   indicator light says.

Frequently Asked Questions

How can I check the air quality inside my house?

A consumer PM2.5 monitor is the practical option — it measures particulate directly in the room rather than reporting a city-wide outdoor figure. Placed sensibly and used to watch changes rather than to obtain a precise absolute number, it tells you what outdoor AQI apps cannot.

Is indoor air worse than outdoor air?

Often, and that surprises people. Homes add their own sources — cooking, incense, candles, cleaning products, off-gassing furniture — on top of outdoor particulate that infiltrates continuously. During and after cooking, a kitchen can be the worst air in the building even on a moderate outdoor day.

Are cheap air quality monitors accurate?

For absolute precision, no. Most consumer devices use laser light-scattering, which estimates particle mass rather than measuring it directly, and readings drift with humidity. For the purpose that matters — spotting changes, seeing what cooking does, confirming a purifier works — they are accurate enough, provided you treat trends as the signal rather than any single figure.

What is a good indoor PM2.5 level?

Lower is better and there is no threshold below which particulate is harmless. As a practical benchmark, WHO guidance puts the recommended annual average well into single digits in micrograms per cubic metre. Most Indian homes will not hold that year-round; a realistic goal is keeping the room you sleep in substantially below the outdoor figure.

Do I need an air quality monitor if I have an air purifier?

Not strictly, but it is the only way to know whether the purifier is doing anything in your particular room. Built-in indicators on purifiers are often coarse and self-reported. An independent monitor is what tells you whether the unit is correctly sized and whether the filter still works.