Delhi's AQI stood at 117 on 31 October 2026 and reached 324 on 2 November, and CAQM invoked GRAP Stage II that day. For AC care before Diwali in Delhi, that two-day jump sets the deadline.
Get the outdoor coil washed, dry the unit and switch it off at the MCB while the air is still fairly clear, then leave it alone. 2025 ran the same way.
On 19 October 2025, Diwali eve, CPCB showed Delhi's AQI at 296 by 4 pm and Anand Vihar at 430 as CAQM brought in Stage II, so a final clean belongs before that point.
The AC service and repair in Delhi page lists what each job covers, and our AC guides hub has related reading.
Photo: A Delhi flat's balcony on a hazy evening before Diwali, with the AC outdoor unit on its bracket
Why the outdoor unit takes the worst of it
An outdoor unit is a fan pulling city air through a block of thin metal fins. While the AC cools, that fan drags far more air across the coil than would ever drift onto it, so one cooling afternoon in heavy smog should load the coil faster than an idle week.
That's reasoning from how the machine works, and it's why we'd stop cooling before the haze arrives instead of cleaning after Diwali week.
What lands on the fins in Delhi also behaves differently from plain dust.
An IIT Madras-led study found chloride to be the highest inorganic fraction in the region's particulate matter, and the ammonium chloride it forms sharply raises how much water those particles take up.
Diwali adds its own mix. A Delhi study accepted by Atmospheric Pollution Research recorded PM2.5 at about 16 times its pre-firework level, with metals such as barium and strontium peaking during the fireworks.
CPCB and DPCC data analysed by Climate Trends put the 2025 average at 488 µg/m³ in the hours after Diwali, a 212% rise on the level before it.
We couldn't find a study measuring what this does to an AC coil in Delhi, so this part is judgement: a salty, water-loving film on metal fins through months of foggy mornings is a deposit we'd want gone first.
The nzeb.in guidance on room ACs, which also explains the BEE star label, says outdoor coils need regular dust removal because efficiency drops in dusty conditions.
Is Diwali the worst of it?
No, and the numbers cut against the festive panic. Diwali AQI was 328 in 2024 and 312 in 2022, yet 218 in 2023.
In 2026, 30 October logged an AQI of 60, the cleanest October day in four years, three days before Stage II.
The worst may also come later. CSE found December 2025 smog more intense and widespread than the two months before, with Delhi's PM2.5 up 29%.
So treat Diwali as a deadline. It falls before the chilly December and January nights the IIT Madras team tied to this chemistry, and the days are usually still warm enough for a washed unit to dry.
What AC care before Diwali in Delhi involves
Do these in order, because a cover over a damp, dirty coil just keeps both in place.
- Pick your last cooling day. In the third week of October 2026, IMD expected days of 31 to 35°C while nights had already dropped to 17.1°C, so some afternoon use is normal. Give it an end date all the same.
- Clean the indoor and outdoor units. The outdoor coil needs a technician in most flats.
- If nobody is servicing the AC this year, wash the filters yourself. Soap and warm water usually clears them, and a damaged filter needs replacing. Let them dry fully before refitting.
- Run Fan mode to dry the inside. One LG owner's manual asks for 3 to 4 hours before a long break; check your own manual, since timings differ by model.
- Cut the power at the MCB or the plug, because the remote only puts the AC on standby. If that MCB feeds other things, unplug the AC instead. If the breaker trips or the socket feels warm, get an electrician in Delhi to look at it.
Photo: A man in a Delhi flat rinsing an AC mesh filter under a tap
Should you cover the outdoor unit?
Only if it sits somewhere dust collects, and only with a fitted fabric cover. A plastic sheet tied around a unit holds damp against the metal, which is the last thing a Delhi coil needs in fog season.
Fitted polyester covers exist for this, such as the dust cover Panasonic sells in India. Fit one only on a clean, dry unit with the power off.
Then take it off before the first switch-on, because the outdoor unit needs clearance around it to perform.
Photo: A fitted fabric dust cover on an AC outdoor unit on a foggy winter morning
Where DIY stops
Filters and Fan mode are yours. The coil wash usually isn't, since many Delhi outdoor units hang on wall brackets or sit outside window grills, and that makes it a height job with water near electrics. The LG manual above leaves even the drain pan to a professional.
Keep the power off before any water goes near the AC, and don't lean past a railing or grill to reach a unit.
Need AC service or repair in Delhi?
See what each visit covers and the price before you book.
Do you need a gas refill before winter?
Almost certainly not.
An iFOREST survey found about 40% of households refilling every year, while the group says a refill should be needed about once in five years.
Gas runs in a sealed loop, so low gas points to a leak, and a top-up before months of no cooling buys you nothing. Ask for the pressure reading during the service and pay for a refill only if it's low.
What the job takes and what it costs
A foam-jet service takes about 45 minutes for one AC, longer for two or more. Keep a tap and a power point nearby, and make sure someone can open the balcony or terrace.
FixThat's catalogue prices for this time of year:
| Job | What it covers | Pick it when | Price |
| Foam-jet service, 1 AC | Indoor foam wash, outdoor coil cleared, cooling check | You want one final clean before shutdown | ₹599 |
| Annual Saver plan, 1 AC | Two planned services across 12 months | You want a pre-Diwali visit and a pre-summer one | ₹1,098 |
| AC Repair, less or no cooling | A repair visit for weak cooling | The AC struggled all summer | ₹299 |
| Gas refill & check-up | Leak test, vacuum, full refill, cooling test | A test shows the gas is low | ₹2,800 |
Three common homes show how this adds up:
- A 2BHK with two ACs has one clean bill: the two-AC foam-jet rate is ₹1,098 for both.
- A 3BHK with three ACs, one of which cooled weakly all summer, pays ₹1,497 for the three-AC foam-jet plus ₹299 for the repair visit, so ₹1,796 in all.
- A 2BHK that wants winter and summer covered pays ₹1,996 for the two-AC Annual Saver plan, against ₹2,196 for two separate two-AC foam-jet visits. That's ₹200 less, so compare what the plan's services include before choosing.
These totals leave out spare parts. GST and the platform fee come at checkout.
Photo: A technician in a plain dark-navy polo washing an AC outdoor unit on a Delhi builder-floor terrace
A countdown to Diwali
Diwali 2027 falls on 29 October 2027, ten days earlier than 2026's 8 November, so more homes will still be cooling when it comes. Count back from the day:
- 14 days before: fix your last cooling day and note any weak cooling, leaks or noise for the technician.
- 7 to 10 days before: get the clean done. In 2026 the air turned six days before Diwali.
- 3 days before: check the filters are back in, run Fan mode, switch off at the MCB and fit a cover if you're using one.
- Diwali week: leave it off, even on a warm afternoon.
If Diwali is only days away
If the festival is close and GRAP Stage II is already on, the 14-day plan has gone. Take a torch to the outdoor fins first.
If you see a grey film, or the coil hasn't had a wash since before summer, try to get it done before the festival. You can book it through AC service and repair in Delhi with FixThat.
If that isn't possible, wash the filters, run Fan mode for 3 to 4 hours and switch off at the MCB the same day. Then get the coil washed after the festival and before 1 December, ahead of the month CSE found worse last winter.
Sources & References
- Outlook India: Delhi-NCR Moves To GRAP Stage II As AQI Enters 'Very Poor' Category
- Business Today: Delhi's air dips to very poor on Diwali eve, CAQM enforces GRAP Stage II
- Business Today: Delhi's air quality turns hazardous post-Diwali as PM2.5 levels hit three-year high
- IIT Madras: Press release on the chloride and Delhi haze study, 27 January 2021
- Manchanda et al.: PM2.5 speciation in New Delhi around the Diwali fireworks
- Down To Earth: Delhi experienced more intense, widespread smog in December 2025, CSE analysis
- The Week: Delhi records coldest night of month, 19 October 2026
- nzeb.in: Room Air Conditioners
- Mongabay India: Plugging AC leaks is the next step to improving energy and emission efficiency
- General HVAC Solutions India: Can I cover the front of the outdoor unit?
- Panasonic India: Outdoor unit dust cover for 1.5 ton air conditioner
- DNA India: How to clean and pack your AC for the winter season
- LG owner's manual: Care when the AC will not be used for a long time
- People Matters: Central government holiday list 2027
- Paytm: Holidays in November 2026
Amit worked as an AC technician in Ahmedabad for 6 years before moving into technical writing, and holds a diploma in Refrigeration and Air Conditioning from ITI Ahmedabad. He explains AC and cooling faults in plain language any homeowner can follow.
Dr. Verma is a mechanical engineer with 15 years of experience in HVAC systems. Her PhD from IIT Delhi focused on energy-efficient cooling for Indian homes, and she consults for AC manufacturers on product design. She checks that numbers are right and advice is safe.