DISCLAIMER: This guideline is not meant to be referred as medical advices.

One of the serious environmental problem in Xi’an (and also in China) is the air pollution. The indicator for air quality is AQI index. To calculate the AQI, many factors are considered. It is crucial for those who came from the cities with good air quality to understand the basic of air pollution to take appropriate measures to protect your health.

The importance of good air quality.

Being in good health is part of a successful study in XJTU. Like eating clean food, being hygienic, or exercise, avoiding bad air is very important especially to sensitive group. Students coming from other cities that does not have an air quality problem should be aware of this problem. Getting sick because of bad air quality is possible.

How to determine the air quality.

Use the air quality index application

Recommended applications:


  • See if the Chinese people on the street are waring mask. If so, the air quality is seriously bad.
  • If the road visibility is becoming low, it is a sign of bad air quality.

Protecting yourself in-doors

  • Air purifier is a good investment.
  • Closing the windows can reduce the amount of dust, but the effect is very limited.
  • This is the air filter after 6 months in-doors: used air filter

Protecting yourself out-doors

  • Use the mask that can filter PM2.5. One mask can be used for 5-7 days. Buying in volume, it will cost about 5RMB per piece.
  • Using mask without PM2.5 filtration capability is not effective.
  • Avoid being outside for a extended period of time.
  • Avoid exercising outside when the air quality is bad.
  • Being in a vehicle does not protect you from the air pollution.

The 3M Masks

There are different options for 3M masks. Here is how to recognize the model number. You will see the model number as 4 digit number with optional letter at the end. For example 9501V and 9002V. Noted that other brands can also effectively filter PM2.5 as well.

Mask model coding:

Model number: [1][2][3][4][a]
[1][2] = Filtering capacity number in percentage. For example, 90 means it is 90% effective. The highest number you could find is 95%. 
[3] = This number is zero. 
[4] = This number represents the fitting mechanism. 1 is for ear loop and 2 is for over-the-head loop. 
[a] = This value is optional. The letter "V" indicates that the mask as a valve, this may make it easier to breath out. 

9501 = 95% effective, ear loop, without breath-out valve. 
9502V = 95% effective, head loop, breathing valve, sponge at the nose clip. 
9502V = 95% effective, head loop, breathing valve, NO sponge at the nose clip. 

Last Update: February 8th, 2019