About and methodology

What this is

BreatheBetter is a free, non-commercial guide for households in Delhi NCR. It turns public-health and building-science guidance into practical steps and small calculators. It is open source: anyone can copy, translate or adapt it.

What it is not

• Not medical advice. It summarises public guidance for the general public. People with health conditions should follow their own doctor’s advice.
• Not a live air-quality service. We link to official monitoring (CPCB, SAFAR, IITM) instead of repeating numbers that go stale.
• Not a shop. We describe the specifications to look for and never name or rank brands. No ads, no affiliate links, no sponsored content.

How content is sourced

Every page lists its sources and the date it was last reviewed. We prefer primary sources: WHO, India’s Central Pollution Control Board (CPCB), the Commission for Air Quality Management (CAQM), the Ministry of Health’s national programme on climate change and human health, the US EPA and CDC/NIOSH, and peer-reviewed studies. Region-specific facts (AQI breakpoints, GRAP stages, helplines, electricity tariffs) are kept in one data file and re-checked every September, before the pollution season.

Health pages have not yet been reviewed by a clinician. Each page shows its review status. If you are a doctor and willing to review, please get in touch.

How the calculators work

Purifier size

CADR (m³/h) = floor area (ft²) × ceiling height (ft) × 0.0283 × target air changes per hour, rounded up. We suggest 5 clean-air changes per hour as a starting point, which matches the US EPA and AHAM rule of thumb (smoke CADR in CFM ≥ ⅔ of floor area in ft² at an 8 ft ceiling), and 6 for rooms where a sensitive person spends long hours.

Running cost

Electricity uses Delhi's DERC domestic tariff (the FY 2021-22 schedule, still in force) plus surcharges, purchase-cost adjustment and electricity tax: about ₹9 per extra unit above 400 units a month, about ₹3 between 201 and 400 units (subsidised), and ₹0 below 200. Surcharge figures change, so treat these as estimates.

Clean-room simulator

A single-room, well-mixed mass-balance model: indoor PM2.5 changes with outdoor air leaking in (penetration × infiltration rate), removal by the purifier (CADR ÷ room volume), settling onto surfaces (deposition) and any indoor source. It is meant for comparing options, such as sealing versus a bigger purifier, not for predicting a monitor reading. Real homes vary widely. There are no published air-leakage measurements for Delhi homes, so the presets are illustrative values drawn from a review of about 10,000 homes worldwide (Nazaroff, 2021) and a Delhi apartment model (Liao et al., 2019). The “average” preset reproduces the roughly 0.7 indoor-to-outdoor ratio reported in Indian homes.

AQI translator

Uses the published PM2.5 breakpoints for India’s National AQI and the US EPA AQI (2024 revision), with linear interpolation inside each band. Real AQI reports may be driven by other pollutants.

Privacy

No accounts, cookies or tracking. Anything you type into a tool stays in your browser. The household plan is saved in your browser’s local storage so it is there next time, and “Start over” deletes it.

Corrections

Found something wrong or out of date? Open an issue with the page and a source. Corrections are welcome.

Licence

Code under the MIT licence. Written content under CC BY 4.0.