Air Purifier vs Exhaust Fan: Dilution or Removal?

This distinction is worth internalising because it resolves nearly every version of this question. An exhaust fan does not reduce the amount of pollution in the world; it moves it from your kitchen to your street and brings the street's air in exchange. That is an excellent trade when your kitchen air is far worse than the street's, and a bad one when it is not.

A purifier does the opposite. It cannot help with anything ventilation-dependent — it does not touch CO₂, does not remove carbon monoxide, does not dry out a damp bathroom — but it does reduce the actual pollutant load in the air of a sealed room, which no amount of ventilation can do when the outdoor air is the source.

Indian cooking is a serious indoor emission source: high-heat tempering, deep frying and open-flame roasting produce PM2.5 concentrations in an unventilated kitchen that can rival a bad outdoor smog day, plus NO₂ and CO from the gas flame itself.

The correct arrangement is a chimney or a properly sized exhaust fan running during and for ten minutes after cooking — extraction at the source, before the fumes spread — and a purifier in the adjoining living space handling the fraction that escapes. A purifier alone in a kitchen is trying to catch smoke that has already dispersed through the flat.

Carbon dioxide is the clearest example. A closed bedroom with two adults can reach 1,500-2,500 ppm CO₂ overnight, well past the point where measured cognitive performance and sleep quality decline. No purifier reduces CO₂; only fresh air does.

This is the genuine tension in a high-pollution Indian city, and it does not have a clean answer. The honest advice is to ventilate at the least-polluted time of day — usually early afternoon rather than early morning, when the inversion has lifted — and let the purifier bring the particulate load back down afterwards.