Vietnam Air Quality by City: When to Wear a Mask and What to Know

When pollution actually hits Vietnam

Vietnam (베트남 / 越南 / ベトナム)'s air-quality problem is seasonal and hyperlocal. If you're visiting between November and February, especially in Hanoi and the Red River Delta, you'll notice haze. During summer (May–September), most cities clear up. Spring (March–April) is a mixed bag; autumn (October) starts to worsen as agricultural burning picks up in northern regions.

The worst months are typically December through mid-February, when cold air traps pollution near the ground, straw-burning peaks in neighboring Chinese provinces, and vehicle emissions concentrate in still air.

Reading the air-quality index (AQI)

Vietnam uses the U.S. Environmental Protection Agency's Air Quality Index scale (0–500+). You'll see it on local apps and websites:

• 0–50 (green): Good. No mask needed.
• 51–100 (yellow): Moderate. Sensitive people (children, elderly, asthma) might feel it; others won't.
• 101–150 (orange): Unhealthy for sensitive groups. Most travelers won't notice; asthma sufferers should consider a mask.
• 151–200 (red): Unhealthy. You'll see haze. N95 masks recommended if you're outdoors for hours.
• 201–300 (purple): Very unhealthy. Masks essential; consider staying indoors or limiting outdoor time.
• 300+ (maroon): Hazardous. Avoid outdoor activity. Stay inside with windows closed.

On bad days, the AQI in Hanoi (하노이 / 河内 / ハノイ) can spike to 200+ by mid-morning. Saigon rarely exceeds 150.

City-by-city breakdown

Hanoi

Worst overall. The Red River Delta and surrounding coal plants, vehicle traffic (9+ million motorbikes), and geographic trapping make Hanoi a pollution hotspot. December–February AQI regularly hits 150–250. If you're there in winter, check the daily forecast. Mornings are often worse than afternoons (pollution hasn't dispersed yet). Avoid early-morning runs or long outdoor sightseeing on orange/red days.

Saigon (Ho Chi Minh City)

Better than Hanoi, but still significant. AQI runs 80–120 in winter, 40–70 in summer. Motorbike traffic and port emissions are the main sources. Pollution is less visible here than in the north because air tends to circulate more easily. Masks are rarely necessary unless you have respiratory issues.

Da Nang

Mountain-ringed and relatively open to the sea. AQI stays 60–100 even in winter. One of Vietnam's cleanest major cities for air. Masks almost never needed.

Hue

Similar to Da Nang—geographic advantage keeps it cleaner. Winter AQI: 70–110. Summer: 40–60. Not a pollution concern for most travelers.

Hai Phong

Port city north of Hanoi with steel mills and cement plants. Winter AQI: 120–180. Worse than Hanoi on some days due to industrial emissions. If you're visiting from Hanoi to Ha Long Bay, you'll pass through here; a mask during peak hours (early morning, evening commute) is wise in winter.

Ha Long Bay and northern coastal areas

Generally clean due to open water. AQI 60–100 even in winter. Wind helps. Not a mask-wearing destination.

Hoi An

Small, coastal, excellent air quality year-round. AQI 50–90. No mask needed.

Sapa

Highland location (1,600m) means excellent air quality even in winter. AQI 40–70. Tourism masks are unnecessary for air quality; bring a light jacket instead for the cold.

Da Lat

Similar to Sapa—highland, cool, clean air. AQI 40–60 year-round. No pollution concern.

Photo by Atlantic Ambience on Pexels

Choosing and using masks

What to buy

N95 or KN95 masks are the only type worth wearing. Surgical masks and cloth masks do almost nothing for particulate pollution (they block large droplets, not fine PM2.5 particles). A box of 50 KN95 masks costs 80,000–120,000 VND (USD 3.20–4.80) at pharmacies like Pharmacity or Mediplus. Brands like 3M and Korea's LG Airmask are widely available.

Don't overbuy—if you're in Hanoi for a week and AQI is moderate, you might use 2–3 masks. Buy as needed rather than bringing a suitcase from home.

When to wear one

Wear a mask if:

• AQI is 150+ and you're outside for 2+ hours.
• AQI is 100–150 and you have asthma, heart disease, or are under 5 or over 65.
• You're cycling, running, or doing strenuous outdoor exercise on orange/red days.

Don't wear one if:

• AQI is below 100 (it's overly cautious and uncomfortable in humid heat).
• You're indoors with clean air (coffee shops, hotels with decent ventilation).

Fit matters

Masks only work if they seal around your nose and mouth. If you have a beard or facial hair, the seal breaks—trim it or shave before a high-pollution day if possible. Children under 10 find N95s uncomfortable and often pull them off; consider staying indoors instead.

Checking AQI in real time

Vietnam doesn't publish an official government AQI in many cities—it relies on U.S. Embassy air-quality monitors in Hanoi and Saigon (사이공 / 西贡 / サイゴン). Use these apps and websites:

• IQAir (iqair.com or mobile app): Most comprehensive for Vietnam. Real-time AQI for 50+ Vietnamese cities, includes forecasts 7 days out. Free and accurate.
• AirVisual (owned by IQAir): Same data, simpler interface.
• Google Maps: Type "air quality" in search to see local AQI by neighborhood.
• Vietnamese news sites: VnExpress and Thanh Nien sometimes publish daily AQI alerts in winter.

Check in the morning before planning your day. If it's orange or above, adjust your itinerary—visit museums, cafés, or air-conditioned malls instead of open-air sites like Old Quarter walking tours.

Photo by Vietnam Hidden Light on Pexels

Practical daily habits

Indoors: Keep windows closed on bad days. Run an air purifier if your hotel has one (mention it when booking). Most hotels in Hanoi and Saigon now have purifiers in deluxe rooms; budget hotels often don't.

Outdoors: Limit strenuous activity (running, cycling) on red/purple days. Walking, casual sightseeing, and eating at outdoor street-food stalls are fine on orange days (100–150 AQI) for most people.

Throat irritation: If you're sensitive, gargle with salt water at night after a day in haze. Locals swear by it and sell throat lozenges (kẹo ho) at convenience stores for 10,000–20,000 VND.

Common pitfalls

• Overpacking masks: You don't need to arrive with 100 masks. Buy them in Vietnam when you need them. Pharmacies stock them year-round, and stockpiles surge by November.
• Wearing a mask in summer: Not necessary and uncomfortable. Save your concern for November–February.
• Panicking at 120 AQI: That's orange—annoying, not dangerous for a day trip. It's when AQI hits 180+ that serious avoidance is warranted.
• Trusting cloth masks: They won't help. Only N95/KN95 matter.
• Underestimating humidity: Masks feel suffocating when you're also sweating. Wear them only when necessary.

Bottom line

If you're visiting northern Vietnam (Hanoi, Ha Giang, Sapa) in winter, check the AQI before each day; pack 5–10 N95 masks as backup but plan to buy more locally if needed. Most days in Hanoi in winter won't require a mask—it's the 10–15 really bad days that matter. Southern cities and highland areas rarely need them. For Saigon, Da Nang (다낭 / 岘港 / ダナン), and Hoi An, masks are almost never necessary.