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Engineering notes, comparisons, and data on fresh air systems and indoor air quality — written for Indian homes, institutions, and anyone trying to breathe better in Delhi NCR.

Indian family at breakfast with the Gurugram skyline visible through a hazy balcony
Delhi takes 11.9 years off your lifeMore than any major city on earth. What the AQLI number means, why purifiers can't fix most of it, and the one lever every household has.
Hazy Delhi skyline from a balcony
Delhi NCR AQI is a year-round problemNot just winter. Why PM2.5 stays elevated 9 months a year — and what changes between seasons.
Air purifier vs fresh air system — side by side
Are air purifiers enough for Delhi?Purifiers recirculate. They can't reduce CO₂. Why one system per room isn't the answer.
Student studying at night under warm lamp
The CO₂ cliff at 1,000 ppmAbove 1,000 ppm, cognitive performance drops by up to 50%. A sealed bedroom hits 2,500 by morning.
A peaceful bedroom in morning sunlight
CO₂ in a sealed bedroom, overnightEight hours, doors and windows closed, two adults breathing. Measured curve, dawn to morning.
aqi0 fresh air system on a clean wall
Fresh air system vs air purifierA purifier cleans the air already in your room. A fresh air system brings new outdoor air in. Different problems, different physics.
Cutaway diagram of fresh air system mechanics
Positive pressure, explained with a bicycle tyreOutdoor air through HEPA, pushed in at 500 m³/h, holding the home at +10–25 Pa. Same physics as a tyre.

Everything below is written by the aqi0 team based on our own measurements across multiple installs, peer-reviewed research, and real customer conversations. No clickbait, no fluff.

Watch on YouTube

Short narrated walkthroughs on the aqi0 YouTube channel — 7-8 min each, one new video most weeks.

Why Indian homes need fresh air, not air purifiers
Why Indian Homes Need Fresh Air, Not Air PurifiersThe air-purifier-isn't-enough argument, with the CO₂ angle most homes miss.
The myth of the clean season
The Myth of the Clean SeasonWhy Delhi NCR air is bad year-round, including monsoon.
PM2.5 in Delhi NCR — your child inhales 18 times the WHO limit
Why Your Child Inhales 18× the WHO LimitThe cumulative-dose math, mechanism in young airways, and why a purifier alone isn't enough.
Why you wake up tired — CO₂ in your bedroom
Why You Wake Up Tired: CO₂ Hits 2,500 ppm by 6 AMThe maths of a sealed Indian bedroom, what 1,500–2,500 ppm does to sleep, and what fixes it.
Set it and forget it — a fresh air system for Indian homes
Set It and Forget ItOne install, whole home, AMC handles filter changes. You stop thinking about indoor air.
The tadka spike — why Indian kitchens hit 500 µg/m³ in 90 seconds
The Tadka Spike: 500 µg/m³ in 90 SecondsWhy your chimney isn't enough, and the door rule that keeps the rest of your home clean.
Year-round yoga at home — why clean indoor air changes the practice
Year-Round Yoga at HomeThe seasonal pause that breaks most home practice in NCR — and what changes when indoor air stays clean.
Why your air purifier can't handle Delhi winters
Why Your Air Purifier Can't Handle Delhi WintersWhy every premium purifier in NCR stays red or purple from October to February — the math that ends the argument.
Why Indian lungs are 10-15% smaller
Why Indian Lungs Are 10–15% SmallerHow much is genetics, how much is chronic pollution, and what changes when kids grow up breathing clean indoor air.
The 1,000 ppm CO₂ cliff — what indoor CO₂ does to your brain
The 1,000 ppm CO₂ CliffBerkeley Lab and Harvard cognitive studies. Why 1,000 ppm isn't a comfort threshold — it's a performance threshold.
Delhi Takes 11.9 Years Off Your Life. Here's the Part You Can Actually Fix.
Delhi Takes 11.9 Years Off Your Life. Here's the Part You Can Actually Fix.Delhi takes 11.9 years off your life — more than any major city on earth. What the AQLI number means, why purifiers can't fix most of it, and the one part you can actually fix at home.
Can the Body Adapt to Air Pollution? Five Questions Every Delhi NCR Family Asks
Can the Body Adapt to Air Pollution? Five Questions Every Delhi NCR Family Asksthe 'won't my body lose tolerance to bad air?' objection — answered with the household water-filtration analogy, the 'less is better' axiom, and twenty-five peer-reviewed studies. Indoor PM2.5 ten times cleaner during the hours you spend at home
AQI Zero in 10 Minutes - Why Indian Homes Need a Whole-Home Air Purifier
AQI Zero in 10 Minutes — Why Indian Homes Need a Whole-Home Air Purifierthe canonical 10-minute version of the full aqi0 argument — the stakes, the year-round physics, the mass-balance limit of every room purifier, the AQI Zero promise, and the recovery evidence
When Will Indian Air Be Clean? What Reykjavik, London, Beijing and Seattle Tell Us
When Will Indian Air Be Clean? What Reykjavik, London, Beijing and Seattle Tell UsReykjavik already has it. London took 50 years. Beijing made it in 10. Where India sits, the realistic arc to clean Indian air, and what to do for the years in between
What Happens to PM2.5 After You Breathe It In - The Journey from Nose to Bloodstream
What Happens to PM2.5 After You Breathe It In — The Journey from Nose to BloodstreamPM2.5 is not stopped by your nose. It reaches every organ in your body. The journey, the science, and what an Indian family can do about it
Indian Air Has Always Been Over WHO - That's Why The Brand Name Is The Target
Indian Air Has Always Been Over WHO — That's Why The Brand Name Is The TargetIndian air has been over WHO at every metro, every year on record. The trend isn't the story — the constant is. And why that makes indoor air a household infrastructure decision.
Do Higher Floors Have Cleaner Air? Why the 20th Floor Won't Save You From PM2.5
Do Higher Floors Have Cleaner Air? Why the 20th Floor Won't Save You From PM2.5Do higher floors have cleaner air? Barely — fine PM2.5 mixes through a kilometre-deep layer, so even the 20th floor of a Gurugram tower is many times the WHO limit. Why altitude is a false sense of safety.
Won't We Suffocate If We Seal the House? Why Stale Air - Not Oxygen - Is the Real Problem
Won't We Suffocate If We Seal the House? Why Stale Air — Not Oxygen — Is the Real ProblemWon't you suffocate if you seal the house against the smog? No — oxygen barely moves. The real issue is stale air: bedroom CO2 hits 1,500-2,500 ppm by morning, and a recirculating purifier can't fix it. Filtered fresh air can.
Why an Air Purifier Company Wants to Go Out of Business
Why an Air Purifier Company Wants to Go Out of BusinessWhy an air purifier company openly wants to put itself out of business — the name as a target, the good days we cheer for, and the day no home needs us
Can One System Clean the Whole Home? Why a Purifier in Every Room Isn't the Answer
Can One System Clean the Whole Home? Why a Purifier in Every Room Isn't the AnswerOne purifier in the living room isn't enough, and one in every room is expensive and leaves corridors and kitchens uncovered. A single-room purifier is sized for one room — why one whole-home positive-pressure system covers the entire 2-4 BHK at once.
Does Your AC Clean the Air? Why Cooling Isn't Cleaning
Does Your AC Clean the Air? Why Cooling Isn't CleaningRunning the AC with the windows shut feels clean and fresh — but a split AC just recirculates the same indoor air over a cold coil. Its filter is too coarse for PM2.5, and it adds no fresh air, so CO2 still climbs to 1,500-2,500 ppm overnight. Cold air isn't clean air.
Do Salt Lamps, Ionizers & Diffusers Clean Your Air? (Two of Them Make It Worse)
Do Salt Lamps, Ionizers & Diffusers Clean Your Air? (Two of Them Make It Worse)A salt lamp, an ionizer, an oil diffuser — they feel like they clean your air. They don't. The salt lamp does nothing measurable; the ionizer can add ozone and ultrafine particles; the diffuser adds VOCs. None capture PM2.5. Real cleaning means trapping particles and flushing gases — honest mechanical filtration.
How a Whole-Home Air Purifier Actually Works - Every Component, Honestly Explained
How a Whole-Home Air Purifier Actually Works — Every Component, Honestly ExplainedA five-part walkthrough of the aqi0 unit — outdoor intake louver, washable pre-filter, H13 HEPA, EC fan, indoor outlet — following the air outside-to-inside. Plus the one honest decision most brands hide: a standard, off-the-shelf-compatible filter size (no lock-in). Unlike a recirculating purifier it brings in fresh air, so it removes CO2 too — whole-home, one unit, ~30W.

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Fundamentals

A modern sealed Indian apartment with an indoor air quality monitor
Why Your New Home Has Worse Air Than Your Grandmother's: The Sealed-Building ParadoxOlder Indian homes leaked. Modern uPVC homes don't. The same envelope improvement that lowered electricity bills now traps CO₂…
An aqi0 fresh air system installed on an interior wall — louver, intake duct, filter housing and indoor unit
How the aqi0 Fresh Air System Works — Every Component, Honestly ExplainedInside the aqi0 fresh air system: EC fan, two-stage filtration, the 362mm filter decision most brands won't talk about…
Pump and tyre — the analogy aqi0 uses for positive-pressure home ventilation
Positive Pressure Ventilation, Explained — With a Bicycle TyreA positive-pressure ventilation system keeps a home cleaner than the outdoor air around it by pushing filtered air in.
Close-up of an H13 HEPA filter pleat — the core of a fresh air system
What Is a Fresh Air System? A Plain-English Explainer | aqi0A fresh air system replaces indoor air with filtered outdoor air. It reduces PM2.5 and CO₂ simultaneously, unlike purifiers.

Reference

The data, standards, and definitive guides.

Stubble fire in a Punjab paddy field — the autumn ritual that affects Delhi NCR air
Stubble Burning, Explained: The Policy Change That Made It InevitableStubble burning is 4–8% of Delhi's annual PM2.5 — and the 2009 water-table policy made it inevitable.
Air pollution and dementia — the Lancet's 2024 modifiable-risk-factor list
Air Pollution and Dementia: What the 2024 Lancet Commission Actually SaidThe 2024 Lancet Commission added air pollution to its 14 modifiable risk factors for dementia.
Monsoon street in Delhi NCR — why rainfall removes PM10 but not PM2.5
Why Monsoon Doesn't Wash PM2.5 Away (It Only Takes PM10)Rainfall removes PM10 efficiently and PM2.5 much less efficiently. Delhi's 'clean' monsoon air still sits 2–5× the WHO limit.
Lung transplant in India — waitlists, costs, and why prevention is the only real option
Lung Transplants in India: Waitlists, Costs, and Why Prevention Is the Only Real OptionIndian lung transplant programs deliver 85-90% 1-year survival, 50-70% 5-year. Cost ₹20-70 lakh. Waitlist mortality 12–20% because lung donors are scarce.
Indian lung capacity studies — what the spirometry data actually shows
Why Indian Lungs Are 10–15% Smaller Than Western Lungs — and Why It MattersHealthy Indian adults show FVC and FEV1 values 10–15% lower than Caucasian references (Agarwal & Salvi, ERJ 2020).
11,000 litres of air a day — the math of pollution inhaled per Delhi resident
11,000 Litres of Air a Day: How Much Pollution an Average Indian Actually InhalesAn average adult inhales ~11,000 litres of air per day. In Delhi NCR at 100 µg/m³ PM2.5…
Gurugram playground in winter haze — the sector-to-sector PM2.5 gradient
NCR Pollution Micro-Zones: Why Gurugram Sector 56 Is Not the Same as Sector 47A 5 km move within Gurugram can shift your daily PM2.5 exposure by 30–50 µg/m³.
Green firecrackers — CSIR-NEERI certified, 30% lower particulate, still not zero
Green Firecrackers, Explained: What CSIR-NEERI Actually Changed, What It Didn'tCSIR-NEERI green firecrackers reduce particulate emissions by ~30% vs conventional. Still produce PM2.5, still produce noise, still produce festival peaks.
Heavy diesel freight on Delhi's freight corridor — the 2-4 AM pollution spike
The 3 AM Pollution Spike: Why Delhi's Night Air Is Worse Than You ThinkDelhi's worst-AQI hour is 2–4 AM. Heavy diesel freight transits the city overnight, when commercial-vehicle bans lift.
Delhi winter morning inversion — warm-air lid trapping cold smoke beneath
Temperature Inversion: Why Delhi's Winter Air Gets Trapped Just Above Your HeadDelhi's winter air gets trapped under a warm-air lid 100–500 metres up. Same emissions, much higher concentration.
Delhi NCR's skyline — the consolidated source-apportionment picture
Where Delhi's PM2.5 Actually Comes From: The 2024–25 Source-Apportionment MapFive major source-apportionment studies of Delhi PM2.5 — IIT-Kanpur 2015, TERI 2018, CEEW 2023 and others…
Cumulative pollution effect — why every year of clean air still counts
The Cumulative-Damage Model of Air Pollution: Why Every Year of Clean Air Still CountsA 40-year Delhi NCR resident has inhaled ~16–24 grams of PM2.5 — about half of it permanently retained.
Gurugram's continuous construction boom — the under-discussed source of NCR PM10 and silica
Construction Dust in Delhi NCR: Why Gurugram's Air Is Often Worse Than Delhi'sGurugram's continuous construction boom adds PM10 and silica to NCR air. ~8% of Delhi-NCR PM2.5 from construction (CEEW 2023).
Indian office in afternoon — CO₂ levels climbing past the WHO 1,000 ppm guideline
The 1,000 ppm CO₂ Cliff: What the Science Actually Says About Indoor CO₂ and Your BrainThe 2012 Berkeley Lab study and 2016 Harvard CogFx work both showed measurable cognitive drops at indoor CO₂ levels routine in Indian…
Brick kiln chimney in the Delhi NCR industrial belt — 6–7% of regional PM2.5
Brick Kilns Around Delhi: The Seasonal Pollution Source Most Maps Don't Show3,000+ legal brick kilns ring Delhi-NCR, contributing 6–7% of regional PM2.5. The zigzag-technology transition is real but uneven.
Sun through a clean window — what the world's cleanest-air cities have in common
Best AQI Cities in the World 2026: What Reykjavik, Helsinki and Sydney Do That Delhi Doesn'tReykjavik, Helsinki, Sydney, Auckland — only 17% of global cities meet the WHO PM2.5 guideline.
Indoor air quality monitor in an Indian bedroom showing elevated overnight CO₂
Bedroom CO₂ at Night: Why It Climbs Past 1,400 ppm — and What It Does to Your SleepTwo adults in a closed Indian bedroom hit 1,400+ ppm of CO₂ by midnight.
Three phones, three different AQI numbers — CPCB vs IQAir vs WAQI methodology
Why Your Phone's AQI Disagrees With Your Monitor: CPCB vs IQAir vs WAQI MethodologyIndian CPCB AQI of 244 = US/IQAir AQI of 174 = same PM2.5 of 100 µg/m³.
Indian endurance athlete training in NCR haze — the cost air pollution levies on sport
Olympic-Medal Poverty: Why Air Pollution May Be Costing India Sporting MedalsIndia's per-capita Olympic medal count is one of the lowest globally. Indian lung capacity is 10–15% below GLI references.
PM2.5 and type 2 diabetes — the under-discussed mechanism in India
Air Pollution and Type 2 Diabetes: The Link No One Talks About in IndiaA 2022 Lancet Planetary Health analysis attributed roughly one in five global type 2 diabetes cases to PM2.5.
Air pollution and fertility — what the 2024–25 evidence shows for Indian couples
Air Pollution and Fertility: What the 2024–25 Evidence Shows for Indian CouplesA 2025 study across 120 Indira IVF centres found men in AQI > 151 regions had 11% lower normal sperm DNA integrity.…
Delhi skyline through smog — outdoor reality, indoor opportunity
Delhi Air Pollution: What Actually Works at Home (2026)Honest field guide to Delhi air pollution at home. What works (mechanical ventilation + HEPA), what doesn't (masks indoors, plants, ionisers)…
Sunlight through a bedroom window — what well-ventilated sleep should look like
CO2 in Your Bedroom: The Overnight Problem Nobody Talks AboutClosed bedrooms hit 1,200-2,500 ppm CO₂ overnight. WHO guideline is 1,000. Above that, decision-making drops 15-50%. The science, and the fix.
An Indian mother and her young child look out through a clean apartment window onto a bright clear blue sky over a modern Indian residential skyline — the future India is moving towards, and the indoor air every family can have today
When Will Indian Air Be Clean? What Reykjavik, London, Beijing and Seattle Tell UsIndia will reach WHO air-quality levels one day. Reykjavik already has. London took 50 years. Beijing made it in 10.
Sunrise over a clean Indian home — what good indoor air quality looks like
PM2.5 Safe Levels in India: WHO vs CPCB, Explained (2026)WHO says 15 µg/m³. India's CPCB says 60 µg/m³. Most Indian cities exceed both.
A modern sealed Indian apartment with an indoor air quality monitor — the gap between feeling clean and being clean
Indoor Air Quality in India: What It Means, Why It's Worse Indoors, and What WorksIndoor air in most Indian homes is worse than people think. PM2.5 tracks outdoor pollution within an hour.
Indian family at breakfast in a softly-lit dining space, mother in cotton kurta, school-bag by the door
Indian air has been over WHO for as long as we've measured it | aqi0Every major Indian metro, every year on record, has reported PM2.5 7-30× over the WHO safe limit.
Delhi NCR skyline through year-round haze — reminder that air quality doesn't follow the news cycle
Delhi NCR AQI Year-Round: Why "Moderate" Air Is Still Hurting YouSummer AQI 80-100 feels safe after winter's 400. It isn't. The annual cycle, why monsoon doesn't fix PM2.5…
Indian children playing on the floor at home — a typical scene where indoor air quality matters most
Air Pollution and Children's Health in India: What Every Parent Should KnowPM2.5, CO₂ and developing lungs — the data on what Delhi air is doing to Indian children…

Practical guides

VOCs in Indian homes — from furniture, paint, sprays, candles and more
VOCs in Indian Homes: A Plain-English Guide to the 1,200-Compound ProblemIndian indoor air contains over 1,200 VOCs from furniture, paint, deodorant, room fresheners and mosquito repellents. Indoor concentrations run 2–5× outdoor.
Plug-in air freshener — the continuous indoor VOC source most Indian homes never question
What's Really in That Room Freshener: VOCs, Phthalates, and the Indoor-Air Cost of Smelling FreshAir fresheners contain phthalates (86% of products tested, NRDC 2007), formaldehyde, and 1–8 hazardous chemicals per product.
Pregnancy in Delhi NCR — what PM2.5 does to the developing foetus, trimester by trimester
Pregnancy in Delhi NCR: What the Air Does, Trimester by TrimesterPM2.5 exposure during pregnancy raises odds of low birth weight 1.4× and preterm delivery 1.7× (2025 Indian national data).
A newborn in an Indian nursery — the first-year air-quality plan
The Newborn's First Year in Delhi NCR: A Practical Air-Quality PlanA baby in NCR spends 20+ hours a day indoors during the first six months.
Inside a new car — the 150-VOC mix you breathe driving home from the dealership
Why a New Car Smells: The 150 VOCs You're Inhaling on the Way HomeThe 'new car smell' is 150+ VOCs from plastics, foams, adhesives.
Mosquito coil and liquid vaporiser — the indoor smoke most Indian homes use
Mosquito Coils, Liquid Vaporisers and Mats: The Indoor Smoke You're ChoosingOne mosquito coil emits PM2.5 equivalent to 75–135 cigarettes (chamber study, 2019). Liquid vaporisers release pyrethroids continuously into bedrooms.
New memory foam mattress — the VOCs that emit through the first month
What Your New Mattress Off-Gases for the First Month (and What CertiPUR Actually Means)A new memory foam mattress emits VOCs for weeks. CertiPUR-US certification limits this. Indian brands (Wakefit, Sleepwell, Sleepyhead) vary in disclosure.
Low-VOC paint in an Indian living room — Asian Paints, Berger, Dulux, Nerolac options
Low-VOC and Zero-VOC Paints in India 2026: Brand-by-Brand Buyer GuideIndian premium brands now offer credible low-VOC paint at 5–15% cost premium.
Indian kitchen with door closed during cooking — the protocol that keeps the rest of the home clean
Why the Kitchen Door Should Stay Closed When You Cook (in a Sealed Indian Home)Cooking PM2.5 spikes to 500–3,000 µg/m³ during tadka. With the kitchen door open, it spreads through the home in minutes.
Indian kitchen during tadka — the moment chimney and exhaust performance matter
Kitchen Chimney vs Wall Exhaust Fan: Why One Works and the Other Is Mostly DecorationA wall-mounted exhaust fan removes Indian-cooking pollutants. A recirculating overhead chimney mostly doesn't.
Money plant leaf with PM2.5 dust deposits — why plants don't clean indoor air
Why Money Plants Stop 'Breathing' in Delhi Winter (and What the NASA Study Really Said)The 1989 NASA Clean Air Study has been misread for 35 years. To match the chamber result in a real living room…
Indoor combustion in Indian homes — every flame is an indoor air problem
Every Indoor Flame Is an Indoor Air Problem: Tandoor, Sigri, Diya, Gas BurnerEvery indoor flame is an indoor-air problem — gas burner, sigri, tandoor, diya, agarbatti.
Newly-unboxed MDF furniture — the silent source of formaldehyde in Indian homes
Formaldehyde from MDF and Particleboard Furniture in India: What You're Actually BreathingMDF and particleboard furniture release formaldehyde — IARC Group 1 carcinogen — for years after installation.
Aerosol deodorant spray — the 2-second VOC spike inside an Indian bathroom
The Two-Second Spike: What an Aerosol Deodorant Does to Your Bathroom AirIndependent testing has found benzene contamination up to 17.7 ppm in aerosol body sprays (Valisure 2021).
Indian child doing homework at a desk — second-hour focus and indoor CO₂
Why Your Child Loses Focus in the Second Hour of Homework — It's Not Screen TimeA child doing homework in a closed bedroom is breathing 1,500+ ppm CO₂ by the second hour.
Carpet and indoor air — the long-term dust mite and allergen reservoir
Carpets and Indoor Air: VOCs, Dust Reservoirs, and What to Ask Before You Lay Wall-to-WallNew carpet emits 4-PCH for weeks. Fitted carpet then acts as a long-term dust-mite and allergen reservoir.
Agarbatti burning during puja — the PM2.5 source Indian families light themselves
Candles, Incense and Agarbatti: The PM2.5 You Light YourselfPM2.5 during dhoop burning in a closed puja room can exceed 1,700 µg/m³.
Bathroom exhaust fan — the 60-second tissue test to check airflow
The Bathroom Exhaust That Doesn't Exhaust: A 60-Second Tissue TestMost Indian bathroom exhaust fans look like they're working. Many move almost no air.
Alum stone (फिटकरी) — India's centuries-old natural deodorant
Alum (फिटकरी) as a Natural Deodorant: The ₹20 Stone That Lasts Four YearsFitkari — potash alum — has been India's natural deodorant for centuries. ₹20 for 4 years.
Elderly Indian with an inhaler — non-smoker COPD and the silent decline
Air Pollution and Your Parents: COPD, IPF, and the Silent Decline No One Talks About12 million Indians have COPD — half of cases non-smoking, driven by biomass cooking and outdoor PM2.5.
Indian woman doing morning yoga in a bright apartment with greenery through the balcony window
Year-Round Yoga at Home: Why Clean Indoor Air Changes the PracticeMost Indian yogis cut back on home practice from October to February. The reason isn't motivation — it's the air.
Sunlight through a home window — what clean indoor air should look like
How to Reduce PM2.5 at Home in India: 10 Methods, Ranked HonestlyTen ways to reduce PM2.5 inside an Indian home, ranked by how much each actually works. Houseplants: 0.

Comparisons & decision guides

HEPA filter grades H11, H13, H14 — what the numbers actually mean for Indian homes
HEPA Filter Grades H11, H13, H14 in India: What the Numbers Mean and Which You NeedH13 captures 99.95% of the most-penetrating particle size. H14 captures 99.995% — 10× less leakage but with airflow and energy penalties.
Macro close-up of pleated H13 HEPA filter media
Fresh Air System Filter Change Guide — How Often, By Whom, What Happens If You SkipTwo-stage filtration in a fresh air system: washable pre-filter every 7-10 days (DIY), H13 HEPA every 45-90 days (AMC).
ERV vs HRV vs PPV — which ventilation system fits an Indian home
ERV vs HRV vs PPV: Which Ventilation System Fits an Indian Home?HRV was designed for cold climates. ERV for humid climates. PPV — positive-pressure ventilation — was built for polluted outdoor air.
EC backward-curved centrifugal fan motor — the kind aqi0 uses inside every fresh air system
EC Fan vs AC Fan — Which One Belongs in a Fresh Air System?EC fans run 24/7 on ~30 W; equivalent AC fans pull 80–120 W. The efficiency gap, the lifespan gap…
Carbon filter held against daylight — the 30-second test that reveals real adsorption
The Carbon Filter Daylight Test: How to Tell If Your Air Purifier's Gas Filter Is RealHold your air purifier's carbon filter against a strong light. If you can see through it, the carbon stage is theatre.
Air purifier showroom — CADR ratings and what they actually measure
CADR Ratings Are Misleading in India — Here's the MathCADR is a 20-minute sealed-chamber test from the 1980s. It ignores ultrafine particles, gases, real-room infiltration, and operating at sleep-mode speed.
Air purifier and fresh-air system side by side — what each one actually does
Fresh Air System vs Air Purifier: The Long Answer With CO₂ MathA purifier removes PM2.5 from one room. A fresh air system addresses PM2.5, CO₂ and VOCs across the whole home…
Gurugram skyline under winter smog — the outdoor concentration that defeats indoor purifiers
Why Your Air Purifier Can't Handle Delhi Winters: The Mass-Balance ProblemIndependent Delhi testing shows premium air purifiers reduce indoor PM2.5 by only 49% when outdoor AQI is high…
A closed window in a Delhi home — the dilemma of fresh air when outdoor AQI is high
Are Air Purifiers Enough for Delhi? Honest Answer (2026)Short answer: no, not for a whole-home year-round solution. Longer answer: it depends on your space, family…

Recently published

Newer deep-dives — automatically listed as each post goes live.

A three-generation Delhi family at breakfast in a clean modular kitchen, with the household water filter visible by the sink — the everyday upgrade that already exists for water
Can the Body Adapt to Air Pollution? The Five Questions Every Delhi NCR Family AsksWill my body lose toughness if I run clean air at home? Are my parents already 'adjusted' to Delhi air? Shouldn't my…
An Indian pulmonology research lab — spirometry workstation, lung CT lightbox, peer-reviewed journals on the desk; the literature in context
The Science of PM2.5 and Tolerance: 25 Peer-Reviewed StudiesThe technical companion to "Can the Body Adapt to Air Pollution?"…
Balcony view through Delhi NCR winter haze — the cities at the top of the worst-AQI rankings
Worst AQI Cities in India 2026: Byrnihat, Begusarai, Delhi, and the Rotating Top SlotsByrnihat (Assam-Meghalaya) held the global #1 most-polluted spot in 2024 at 128 µg/m³ annual PM2.5.
PM2.5 reaches every organ — what the science shows about air pollution and the body
What Happens to PM2.5 After You Breathe It In: The Journey from Nose to BloodstreamPM2.5 isn't stopped by your nose. It reaches the alveoli, crosses into the bloodstream, and circulates to every organ.

Live AQI for your city

Updated continuously — what’s in the air right now, what the number means, and what to do about it.

What’s coming next

One new deep-dive most weeks. Follow on YouTube, Instagram, or X to see new posts as they go live, or WhatsApp +91 9667672740 to subscribe directly.

Core references

Something you want us to cover?

If there’s an aspect of indoor air quality, HEPA, ventilation, or aqi0’s product that you’d like us to write up — reply on WhatsApp or email [email protected]. We add reader-requested questions to the calendar every month.