AQI 300+: What a Respiratory Disease Specialist in Delhi Wants Every Family to Do Right Now
Written by Dr. Dixit Kumar Thakur
I am Dr. Dixit Kumar Thakur, Senior Pulmonologist and Respiratory Disease Specialist at Pulmovista Clinics, Delhi. In 13 years of clinical practice in this city, I have lived through more AQI 300+ events than I can count — and I have seen, with painful clarity, what they do to lungs that are unprepared.
When the Air Quality Index climbs above 300 — the threshold that marks the transition from ‘Very Poor’ to ‘Severe’ air quality — the concentration of PM2.5 in Delhi’s air reaches levels that cause measurable, acute biological damage to the airways even in healthy adults. For patients with asthma, COPD, interstitial lung disease, heart disease, or any chronic respiratory condition — AQI 300+ is a genuine medical emergency in slow motion.
This is my personal guide — written as your respiratory specialist, not as a government advisory — on exactly what AQI 300+ means for your health, what it does to your lungs, and what every Delhi family needs to do right now to protect themselves and their loved ones. Share it. Print it. Save it on your phone. The next AQI spike will not wait for you to be ready.
1. Understanding AQI: What the Numbers Actually Mean for Your Lungs
The Air Quality Index (AQI) is a standardised scale that converts complex air pollution data into a single number, making it easier to understand health risk. But most people do not know what the categories actually mean in biological terms — what is happening inside your airways at each AQI level. As a respiratory disease specialist, here is what those numbers mean to me:
AQI Level
Air Quality Category
What It Means for Your Respiratory Health
0–50
Good
Air quality poses little or no risk. Safe for all outdoor activities.
51–100
Satisfactory
Acceptable quality. Unusually sensitive individuals may experience minor symptoms.
101–200
Moderate
Sensitive groups (asthma, COPD, elderly, children) may experience symptoms. Limit prolonged outdoor exertion.
201–300
Poor
Everyone may begin to feel health effects. Sensitive groups at serious risk. Avoid outdoor exercise. Check inhalers.
301–400
Very Poor
Health effects for ALL groups. Significant aggravation of respiratory disease. Stay indoors. Run HEPA purifier. Medical emergency for vulnerable patients.
401–500
Severe / Hazardous
Serious health effects even in healthy people. Life-threatening for chronic respiratory patients. Emergency action required. Contact Pulmovista Clinics if breathless.
>500 (off-scale)
Hazardous — Beyond AQI
Catastrophic air quality — as seen during severe Diwali events and worst stubble-burning days. Equivalent to smoking 40+ cigarettes in a single day. Do NOT go outdoors under any circumstances.
PM2.5: The Specific Pollutant Driving Respiratory Emergencies in Delhi
When the AQI crosses 300 in Delhi, the primary driver is almost always PM2.5 — fine particulate matter with a diameter of 2.5 micrometres or less. To put this in perspective, a human hair is approximately 70 micrometres in diameter. PM2.5 is 28 times smaller — invisible to the naked eye, able to bypass every natural filter in your nose and throat, and capable of penetrating deep into the smallest air sacs of the lung.
At AQI 300, PM2.5 concentrations in Delhi’s air typically range from 150–250 µg/m³. The WHO annual guideline is 5 µg/m³. The WHO 24-hour guideline is 15 µg/m³. During an AQI 300+ event, Delhi residents are breathing air with PM2.5 concentrations 10–50 times above what the WHO considers safe for a single day — for an entire day, sometimes an entire week.
2. What AQI 300+ Does to Your Airways: The Biology You Need to Understand
This section is the most important one in this guide — because understanding what is happening inside your body during a severe pollution event is what motivates the right protective action. As a respiratory disease specialist at Pulmovista Clinics, here is the biology I explain to my patients:
In Healthy Adults — ‘Nothing’ Is Not True
Even in a completely healthy adult with no respiratory history, breathing AQI 300+ air for a full day causes measurable biological changes:
• Acute airway inflammation: PM2.5 particles trigger the release of inflammatory cytokines (IL-6, IL-8, TNF-alpha) from airway epithelial cells within hours of exposure — similar to the early stages of an acute infection.
• Oxidative stress: Ultra-fine particles carry reactive oxygen species (free radicals) on their surface. These directly damage cell membranes, DNA, and the protective mucus layer lining the airways.
• Transient reduction in FEV₁: Studies measuring lung function before and after high-pollution days consistently show reductions in FEV₁ of 3–8% even in healthy young adults after a single AQI 300+ day.
• Cardiovascular effects: PM2.5 that penetrates to the alveolar level crosses into the bloodstream — increasing systemic inflammation, promoting platelet aggregation, and increasing acute cardiovascular event risk within 24–48 hours of severe exposure.
In Asthma Patients — An Acute Attack Waiting to Happen
For asthma patients, AQI 300+ is one of the highest-risk events of the year. Here is exactly why:
• PM2.5 amplifies airway hyper-reactivity: Already sensitised asthmatic airways respond to PM2.5 exposure with increased mast cell degranulation — releasing histamine, leukotrienes, and prostaglandins that cause immediate bronchospasm.
• Ozone synergy: Delhi’s AQI 300+ events frequently coincide with elevated ozone — particularly in the afternoons following sunny, windless days. Ozone independently triggers bronchospasm and, combined with PM2.5, creates a far more damaging exposure than either alone.
• Steroid resistance: Chronic PM2.5 exposure drives neutrophilic airway inflammation that partially resists inhaled corticosteroids — meaning your regular controller inhaler may be significantly less effective during an AQI 300+ event.
• Late-phase response: Even if the immediate bronchospasm from PM2.5 is controlled with a rescue inhaler, the eosinophilic late-phase inflammatory response 4–8 hours later may be more severe — causing dangerous nocturnal deterioration in asthma patients who went to bed feeling ‘okay.’
In COPD Patients — The Exacerbation Trigger
COPD exacerbations — acute worsening episodes that account for the majority of COPD hospitalisations and a significant proportion of COPD mortality — are directly triggered by air pollution spikes. At Pulmovista Clinics, I see COPD exacerbation admissions rise by 30–50% in the 72 hours following a severe AQI event. The mechanism:
• Impaired mucociliary clearance: PM2.5 paralyses the cilia that sweep the airways — allowing bacterial colonisation and viral invasion in already-damaged COPD airways.
• Acute-on-chronic inflammation: PM2.5 adds an acute inflammatory insult on top of the chronic airway inflammation of COPD — pushing already-borderline patients into overt exacerbation.
• Hypoxaemia: In advanced COPD, even mild worsening of airflow can push the patient into acute respiratory failure — particularly at night when respiratory drive is reduced.
In Children — Developing Lungs at Greatest Risk
Children breathe faster than adults — inhaling proportionally more PM2.5 per kilogram of body weight for the same outdoor exposure time. Their lungs are still developing until their mid-20s, and PM2.5 exposure during childhood causes permanent reductions in lung function growth — a deficit that follows them for life. Multiple Delhi-based studies have documented that children in high-pollution Delhi neighbourhoods have lung function measures significantly below predicted values for their age, height, and sex.
🌫 Dr. Dixit Kumar Thakur’s Clinical Reality: What AQI 300+ Looks Like at Pulmovista Clinics On the day after an AQI 300+ event in Delhi, my Pulmovista OPD typically sees: • 2–3 asthma exacerbations that required nighttime rescue inhaler use 5+ times • 1–2 COPD patients in acute exacerbation — increased sputum, worsening breathlessness, reduced SpO₂ • Multiple parents calling about children coughing through the night with no fever — pollution-triggered airway irritation • At least one patient who should have come in during the event but waited too long The pattern is consistent and entirely predictable. Which is why prevention — not reaction — is the only rational strategy.
3. The AQI 300+ Action Plan: What I Tell Every Pulmovista Patient to Do
At Pulmovista Clinics, every patient with a chronic respiratory condition receives a personalised written action plan that includes specific instructions for AQI 300+ events. Here is the core of what that plan contains — presented as a family guide for every Delhi household:
IMMEDIATE Actions When AQI Crosses 300
🚨 IMMEDIATE — Do These the Moment AQI Hits 300 🚨 STOP all outdoor activity immediately — no exceptions for exercise, errands, or school sports 🚨 Close ALL windows and doors — every entry point for outdoor air 🚨 Switch AC/cooler to recirculation mode — NOT fresh air intake 🚨 Turn on HEPA air purifier in your bedroom on maximum setting 🚨 Check all rescue inhalers — are they charged? Not expired? Within reach? 🚨 Asthma patients: take your scheduled SMART maintenance dose NOW if not already taken today 🚨 COPD patients on LTOT: confirm oxygen equipment is working and accessible 🚨 Children with asthma: call school to ensure child stays indoors for all activities
WITHIN THE FIRST FEW HOURS — Prepare Your Home
🏠 Home Preparation During AQI 300+ Events • Seal gaps around doors and windows with wet towels or draft excluders if HEPA purifier capacity is limited • Switch kitchen exhaust to recirculate (not vent outdoors) — cooking fumes on top of outdoor pollution amplify indoor air pollution significantly • Identify your ‘clean room’ — ideally the bedroom with HEPA purifier — where vulnerable family members should spend maximum time • Charge all mobile phones — so you can reach Pulmovista Clinics and emergency services if needed • Gather all medications — inhalers, nebuliser if prescribed, oxygen cylinder if on LTOT — in one accessible location • If you have a portable nebuliser and a standing prescription for nebulised bronchodilator, prepare it — do not wait until symptoms are severe • Keep oral prednisolone standby prescription accessible — for patients Dr. Thakur has prescribed this for
ONGOING — Monitoring and Medication Strategy During a 300+ Event
Patient Group
Dr. Dixit Kumar Thakur’s Medication Strategy for AQI 300+ Days
Asthma — SMART therapy patients
Continue scheduled maintenance puffs. Use additional as-needed puffs at the first sign of any chest tightness, wheeze, or breathlessness — do not wait until symptoms are severe. If you use more than 8 total puffs in a day — call Pulmovista Clinics.
Asthma — traditional ICS + SABA therapy
Take your ICS controller inhaler on schedule. Use Salbutamol rescue at first symptom — 4 puffs via spacer. If partial response only after 4 puffs — take 4 more and call Pulmovista Clinics. Do not manage AQI 300+ attacks alone with SABA only.
COPD patients (GOLD 2–4)
Ensure LAMA+LABA or triple therapy taken. Have SABA rescue accessible. If sputum increases, colour changes, or breathlessness worsens beyond your usual baseline — start written action plan. Contact Pulmovista if uncertain.
Children with asthma
Keep child indoors ALL day. Take maintenance inhaler via spacer on schedule. At the first wheeze, cough, or breathlessness — use rescue inhaler via spacer immediately. Do not wait. Children can deteriorate much faster than adults during pollution events.
Elderly patients with any respiratory condition
This group is at highest risk. Monitor SpO₂ with pulse oximeter if available. Any drop below 94% — contact Pulmovista Clinics or go to hospital immediately. Ensure hydration — elderly patients often under-drink when housebound, thickening airway secretions.
Healthy adults with no known lung disease
Stay indoors. Avoid exercise. If you develop unusual breathlessness, chest tightness, or persistent cough during an AQI 300+ event — do not dismiss it as ‘just the pollution.’ Contact Pulmovista Clinics. You may have undiagnosed respiratory disease that the pollution is unmasking.
4. The Indoor Air Strategy: What Dr. Dixit Kumar Thakur Recommends for Every Delhi Home
The most important thing I tell my Pulmovista patients during AQI 300+ events is this: your indoor air quality is entirely within your control — and the difference between good indoor air and outdoor AQI 300+ air can mean the difference between a stable day and a hospitalisation. Here is my complete indoor air strategy:
The HEPA Air Purifier: The Single Most Important Intervention
A HEPA (High Efficiency Particulate Air) purifier with a true HEPA filter captures 99.97% of particles 0.3 micrometres and larger — including PM2.5, which at 2.5 micrometres is well within the capture range. During an AQI 300+ event, a properly sized HEPA purifier can reduce indoor PM2.5 by 70–90% within 30–60 minutes.
• Room sizing: Match the purifier’s CADR (Clean Air Delivery Rate) to your room size. For a standard bedroom of 150–200 sq ft, a CADR of at least 150–200 m³/hour is recommended. For a living room of 300–400 sq ft, 300–400 m³/hour.
• Filter maintenance: A clogged HEPA filter works at a fraction of its rated efficiency. Check and replace filters every 6 months — more frequently during high-pollution seasons.
• Placement: Position the purifier in the centre of the room or near the breathing zone — not in a corner where airflow is restricted.
• What to avoid: Ioniser-type or ozone-generating ‘air purifiers’ — ozone is itself a respiratory irritant and these devices should never be used by respiratory patients.
N95 Masks: When You Must Go Outside
During AQI 300+ events, staying indoors is the best strategy. But when going outdoors is unavoidable — medical appointments, essential errands, emergencies — an N95 or N99 mask is the only meaningful respiratory protection against PM2.5.
• N95 vs cloth/surgical mask: Cloth masks and surgical masks offer essentially zero protection against PM2.5. They filter large droplets, not ultra-fine particles. Only N95 (or higher) masks filter PM2.5 effectively — when properly fitted.
• Proper fitting is critical: An N95 mask that does not seal against the face provides no PM2.5 protection. Perform a seal check before every use — seal your hands over the mask and breathe sharply. No air should leak around the edges.
• N95 and breathing difficulty: For patients with severe COPD or advanced ILD, the increased breathing resistance of an N95 mask may itself worsen breathlessness. These patients should discuss alternatives — P100 respirators with exhalation valves, or simply avoiding outdoor exposure entirely — with Dr. Dixit Kumar Thakur at Pulmovista.
Indoor Air Pollution Sources to Eliminate During AQI 300+ Events
Counterintuitively, some common household activities make indoor air significantly worse during pollution events — when every source of indoor PM2.5 matters because windows must remain closed:
• Incense sticks and dhoop: A single incense stick burning in a closed room can raise indoor PM2.5 to 500+ µg/m³. During AQI 300+ events — no incense, no dhoop, no agarbatti.
• Open-flame cooking: Gas stoves produce NO₂ and fine particulate matter. Use the range hood, cook with lids on, and — if possible — switch to microwave or electric cooking during the worst pollution days.
• Candles: Even scented candles produce fine particulate matter and VOCs. Avoid during AQI 300+ events.
• Cigarette and hookah smoke: This should be zero inside the home at any time — but during AQI 300+ events, when all ventilation is blocked, even one cigarette indoors creates an indoor catastrophe for respiratory patients.
• Freshly dry-cleaned clothes: Chemical vapours (tetrachloroethylene) from freshly dry-cleaned items — keep them outside or in a closed room away from sleeping areas during high-pollution days.
5. High-Risk Groups: Who Needs the Most Protection During AQI 300+ Events
While every Delhi resident is affected by AQI 300+ events, certain groups face dramatically higher risk and need the most proactive protection. As a respiratory disease specialist at Pulmovista Clinics, these are the patients I am most concerned about during severe pollution events:
High-Risk Group
Why They Are at Greater Risk
Specific Actions Beyond Standard Protocol
Severe or uncontrolled asthma
Steroid-resistant inflammation; high airway reactivity; frequent rescue use means baseline already compromised going into the event
Pre-emptive oral prednisolone standby; urgent Pulmovista review if more than 6 rescue puffs needed; consider stepping up to biologic therapy after the event
COPD Stage 3 and 4
Severely limited respiratory reserve; any additional bronchospasm or mucus can tip into acute respiratory failure; oxygen-dependent patients at highest risk
SpO₂ monitoring every 2 hours during worst days; any drop below 88% — emergency hospital; COPD action plan active from AQI 200+, not 300+
Pulmonary fibrosis (ILD)
Already severely impaired gas exchange; any reduction in alveolar function causes disproportionate breathlessness and hypoxaemia
SpO₂ monitoring; ambulatory oxygen on standby; low threshold for hospital review — ILD patients have almost no reserve
Children under 12 with asthma
Higher respiratory rate; behavioural inability to self-report deteriorating symptoms accurately; school environment may not follow protocols
Keep home from school on AQI 300+ days; call school nurse regardless; monitor continuously; do not delay rescue inhaler
Elderly (>70) with any lung disease
Reduced respiratory reserve; cardiovascular comorbidities amplify PM2.5 cardiovascular effects; less able to communicate symptom severity
Family member or caregiver should physically check on elderly relative twice daily during AQI 300+ events; pulse oximeter monitoring
Pregnant women
PM2.5 crosses the placenta; associated with preterm birth, low birth weight, and foetal lung development impairment
Absolute indoor confinement during AQI 400+ events; N95 if any outdoor exposure unavoidable; contact obstetrician and Pulmovista if respiratory symptoms develop
Immunocompromised patients
On corticosteroids, chemotherapy, or biological immunosuppressants — pollutant-related immune impairment adds to existing vulnerability
Extra vigilance for infection symptoms (fever, purulent sputum) in the days following AQI 300+ events — pollution impairs defences when immune system is already compromised
6. When to Call Pulmovista Clinics vs. When to Go Straight to Emergency
One of the most practically important decisions during an AQI 300+ event is knowing when to manage at home, when to call Pulmovista Clinics for urgent advice, and when to bypass the phone call entirely and go directly to an emergency department. Here is my clear framework:
Manage at Home — If ALL of These Are True
✅ Stay Home and Continue Your Action Plan If: ✅ Your rescue inhaler is providing relief that lasts at least 3–4 hours ✅ You can speak in full sentences without stopping to breathe ✅ Your SpO₂ is above 94% at rest (if you have a pulse oximeter) ✅ You have used fewer than 6 rescue puffs in total today ✅ Symptoms are at your ‘yellow zone’ level — uncomfortable but not deteriorating ✅ You have a written Pulmovista action plan and are following it
Call Pulmovista Clinics Urgently — If ANY of These Apply
⚠ Call Pulmovista Clinics Immediately If: ⚠ You have used 6 or more rescue inhaler puffs in a single day ⚠ Your rescue inhaler is providing relief lasting less than 3 hours ⚠ Breathlessness is worsening despite following your action plan ⚠ Your SpO₂ has dropped to 90–94% at rest ⚠ Sputum has changed colour (yellow or green) or increased significantly ⚠ You are waking repeatedly at night despite rescue inhaler use ⚠ A child has needed rescue inhaler more than 4 times in 24 hours Pulmovista Clinics contact: www.pulmovista.com | Teleconsultation available for patients unable to travel during AQI emergencies
Go to Emergency — Do Not Call First If ANY of These Occur
🚨 GO TO EMERGENCY DEPARTMENT IMMEDIATELY — DO NOT WAIT 🚨 Severe breathlessness — unable to complete a full sentence 🚨 Lips, fingernails, or fingertips turning blue (cyanosis) 🚨 SpO₂ below 90% at rest despite rescue inhaler and home oxygen (if prescribed) 🚨 Rescue inhaler providing no relief after 8 puffs 🚨 Confusion, unusual drowsiness, or decreased consciousness 🚨 Respiratory rate above 30 breaths per minute at rest 🚨 Accessory muscles of the neck and chest visibly straining with every breath 🚨 Child with severe respiratory distress — do not drive, call ambulance
7. After the AQI Drops: What a Respiratory Disease Specialist in Delhi Recommends for Recovery
When the AQI finally returns below 200, the instinct is to immediately open all windows, resume outdoor activity, and return to normal life. As a respiratory disease specialist in Delhi, I urge caution — because the physiological recovery from a multi-day AQI 300+ event takes longer than the pollution takes to clear.
The First 24 Hours After AQI Falls Below 200
• Do NOT immediately resume outdoor exercise: Your airways are still inflamed from the preceding days of high exposure. The first day of ‘cleaner’ air is not the time for a morning run. Wait at least 48–72 hours before resuming outdoor exercise, and start gradually.
• Continue HEPA purifier: Indoor PM2.5 takes several hours to clear even after outdoor AQI improves, particularly in sealed homes. Continue the purifier for at least 24 hours after the AQI returns to acceptable levels.
• Ventilate gradually: Open windows on the side of your home with the lowest traffic exposure, and ventilate for short periods initially — 15–30 minutes — rather than leaving all windows open immediately.
• Monitor symptoms carefully: The late-phase inflammatory response to allergens and irritants peaks 6–12 hours after exposure. Patients who felt stable during the event sometimes experience their worst symptoms in the 24 hours after the AQI drops. Watch for nocturnal worsening.
When to Book a Post-Event Review at Pulmovista Clinics
I strongly recommend that every Pulmovista patient with a chronic respiratory condition books a post-event clinical review within 1–2 weeks of any significant AQI 300+ event that caused symptoms, rescue inhaler use above baseline, or any deterioration in exercise tolerance. This review includes:
• Spirometry — to detect any persistent reduction in lung function from the pollution event
• FeNO measurement — to quantify residual eosinophilic inflammation in asthma patients
• Medication review — to determine whether a step-up in therapy is warranted based on how the patient managed during the event
• Assessment of biologic therapy candidacy — for patients who had 2 or more significant event-triggered exacerbations in the same year
8. Long-Term Protection: What Every Delhi Family Should Have in Place Before the Next AQI Spike
AQI 300+ events in Delhi are not exceptional — they are seasonal, predictable, and recurring. The worst preparation is to be unprepared every time one occurs. At Pulmovista Clinics, I work with every patient to ensure they are equipped before the next event arrives. Here is my long-term protection checklist for every Delhi family:
📋 Dr. Dixit Kumar Thakur’s AQI 300+ Preparedness Checklist — Every Delhi Family 📋 HEPA air purifier with genuine HEPA filter — in bedroom (mandatory) and living room (recommended) 📋 N95 masks — minimum 10 per adult family member; stored in accessible location (not the back of a drawer) 📋 Pulse oximeter — for monitoring SpO₂ during events; particularly important for elderly or high-risk family members 📋 SAFAR-Air or CPCB AQI app installed on every adult’s phone — with AQI 150+ alerts activated 📋 All respiratory inhalers — in date, fully charged, and technique checked at last Pulmovista appointment 📋 Written Pulmovista Asthma/COPD Action Plan — specifically updated to include AQI 300+ instructions 📋 Oral prednisolone standby prescription — for patients Dr. Thakur has identified as eligible for standby steroids 📋 Nebuliser (if prescribed) — checked, cleaned, with adequate medication supply 📋 Home oxygen equipment (if on LTOT) — cylinder full; concentrator serviced; backup cylinder available 📋 Pulmovista Clinics contact number — saved; teleconsultation option understood 📋 Annual spirometry and FeNO at Pulmovista — scheduled; do not skip the pre-season review
9. Why Patients Trust Pulmovista Clinics as Their Respiratory Disease Specialist in Delhi During AQI Crises
When the AQI spikes above 300 in Delhi, my patients at Pulmovista Clinics have something that most Delhi residents do not: a specialist they trust, a written plan they understand, and a direct line to expert respiratory advice. That is what being a patient of a dedicated respiratory disease specialist in Delhi looks like — and it is what I have built Pulmovista Clinics to deliver for over 13 years.
1. Personalised written action plans: Every Pulmovista patient with asthma, COPD, or ILD receives a written action plan that includes specific AQI 300+ protocols — exactly what to do, at exactly what threshold, with exactly what medications. Not a generic leaflet. A personalised plan built from their clinical assessment.
2. Teleconsultation during AQI emergencies: When the AQI is 350 and a patient’s asthma is deteriorating, the last thing they should do is travel through polluted air to reach a clinic. Pulmovista Clinics provides teleconsultation for urgent respiratory review during AQI crises — clinical assessment, prescription adjustment, and escalation decision without leaving home.
3. Pre-season preparation clinics: Before Delhi’s worst pollution seasons — October and November (stubble burning + Diwali) and April–May (dust storms) — Pulmovista Clinics runs pre-season review appointments specifically designed to optimise medication, update action plans, and ensure every patient enters the high-risk period prepared.
4. Biologic therapy for pollution-sensitive severe asthma: For patients who have repeated severe exacerbations during AQI 300+ events, the long-term solution is not more rescue inhalers — it is accurate phenotyping and biologic therapy. At Pulmovista Clinics, I assess and prescribe all five approved biologics for severe asthma, and I initiate this conversation after every significant pollution-driven exacerbation.
5. Environmental counselling integrated into every consultation: Pollution is not a background condition in Delhi — it is an active clinical factor. At Pulmovista Clinics, every consultation includes Delhi-specific environmental advice — AQI monitoring, indoor air quality, N95 mask protocols, and seasonal preparation — because treating the patient without addressing the environment they live in produces incomplete results.
6. GINA 2026 and GOLD 2026 compliant management: The most current international guidelines for asthma and COPD specifically address the role of environmental exposure in disease exacerbation. At Pulmovista, every patient’s treatment plan is aligned with these guidelines — ensuring the most evidence-based, pollution-aware management available in Delhi.
Conclusion: AQI 300+ Is Not Normal — And Your Response Should Not Be
After 13 years of treating respiratory patients in Delhi, I have accepted that we cannot control the AQI. We cannot stop the stubble burning, solve the traffic overnight, or move the city away from its geography. But I refuse to accept that Delhi families must simply suffer through AQI 300+ events without the knowledge, the tools, and the clinical support to protect themselves.
This guide is my contribution to that protection. Share it with your family. Share it with your neighbours. Share it with the parents at your child’s school. Because the families who know what to do when the AQI spikes — who have their HEPA purifier running, their inhalers ready, their written action plan accessible, and their respiratory specialist on speed dial — are the families whose lungs survive Delhi’s worst air days intact.
And if you or anyone in your family has a respiratory condition that has not been fully assessed and managed — the time to act is not during the next AQI 300+ event. It is right now. Book your consultation at Pulmovista Clinics today.
FAQs-AQI 300+ and Respiratory Health in Delhi
How quickly does AQI 300+ pollution affect someone with asthma?
In sensitised asthma patients, the immediate bronchospastic response to PM2.5 and ozone can begin within 15–30 minutes of outdoor exposure. The more clinically dangerous late-phase inflammatory response peaks 4–8 hours after exposure — meaning patients often feel relatively stable during the day and deteriorate significantly overnight. At Pulmovista Clinics, I advise all asthma patients to monitor through the night following any significant outdoor exposure during an AQI 300+ event, regardless of how they feel in the evening.
My child has no history of asthma. Do I still need to keep them home on AQI 300+ days?
Yes — absolutely. Children with no known asthma are still biologically vulnerable to AQI 300+ air. PM2.5 causes acute airway irritation, inflammatory response, and measurable lung function reduction even in healthy children. Repeated high-dose exposure during childhood causes permanent deficits in lung function growth. Additionally, AQI 300+ events frequently unmask previously undiagnosed asthma — children who cough repeatedly, wheeze, or become breathless during pollution events may be experiencing their first identifiable asthma episodes. If your child has repeated respiratory symptoms during pollution events, a spirometry and FeNO assessment at Pulmovista Clinics is strongly indicated.
Is a surgical mask good enough to wear outdoors during AQI 300+?
No. I cannot emphasise this strongly enough. Surgical masks and cloth masks do not filter PM2.5. They trap large respiratory droplets — which is why they are effective for infection control — but PM2.5 particles are orders of magnitude smaller and pass straight through surgical mask material. The only masks that provide meaningful PM2.5 filtration are N95 respirators (which filter 95% of airborne particles) or N99/P100 respirators (even higher filtration). And even N95s must be properly fitted to provide their rated protection — a gap around the nose or chin eliminates most of the benefit.
Should I run my AC during AQI 300+ events?
Yes — but only on recirculation mode, not on fresh air intake. Most split AC units and window ACs have a recirculation setting that cools and circulates indoor air without drawing in outdoor air. This is the correct setting during AQI 300+ events. If your AC only has a fresh air mode, it is better to run a HEPA purifier without the AC than to run the AC in fresh air mode — which will pump outdoor PM2.5-laden air directly into your home. Note also that AC filters are not HEPA grade and do not filter PM2.5 — they only filter larger particles.
My COPD seems stable. Do I need to worry about AQI 300+ if I feel fine?
Yes — and this is one of the most dangerous misperceptions I encounter at Pulmovista Clinics. 'Feeling fine' in COPD patients during pollution events often reflects the fact that COPD patients have learned to reduce their activity to match their respiratory capacity. They feel fine because they are doing less. But their lung function, airway inflammation, and SpO₂ may be deteriorating significantly despite the absence of obvious symptoms. I strongly recommend that all COPD patients — regardless of how they feel — monitor their SpO₂ with a pulse oximeter on AQI 300+ days, follow their written action plan proactively, and contact Pulmovista Clinics at the first sign of any change from their baseline.