Air quality in big Vietnamese cities varies a lot by season and by hour. Hanoi in particular can see high PM2.5 levels from late autumn to early spring. Running remains hugely healthy overall, but on bad days it's smart to adjust.
Check the AQI
The Air Quality Index (AQI) summarises pollution in one number. Check it on IQAir or a similar app before you go out.
- 0–50, Good: run anything
- 51–100, Moderate: fine for most people; sensitive runners take it easier
- 101–150, Unhealthy for sensitive groups: keep it easy and short, especially if you have asthma or heart or lung conditions
- 151–200, Unhealthy: move inside (treadmill, gym) or rest
- 200+, Very unhealthy: skip outdoor exercise
Practical tips
- Timing: pollution often builds up during rush hour and overnight inversions; it is usually lower after rain and on windy days
- Route: parks, lakes and riversides away from main roads are better than busy streets
- Effort: you breathe much more air during intervals than during easy running, so save hard sessions for clean-air days
- Masks: a normal cloth mask does very little; an N95-type mask helps for walking but is uncomfortable for running. Moving indoors is usually the better choice
Have a plan B
Keep a treadmill or gym option, a strength routine or a cycling or swimming session in your back pocket for high-AQI days. Many clubs will message their group if they move or cancel a run because of air quality.