Air Quality Monitor

Thank you for your interest in air quality! This factsheet is divided into three parts: air quality monitoring, why outdoor air quality is important, and Frequently Asked Questions (FAQ).

  • The U.S. State Department, in collaboration with the U.S. Environmental Protection Agency (EPA), puts air quality monitors on some of its facilities to provide information to help protect the health of American personnel and citizens overseas.
  • The U.S. Embassy is responsible for the operation of an instrument that measures particulate pollution with a size of 2.5 microns in diameter or smaller, commonly referred to as PM2.5.
  • Please note that citywide analysis cannot be done with data from a single monitor. This data provides an accurate measure of the air quality for PM 2.5in the section of Hanoi close to the U.S. Embassy.
  • The instrument is at the Embassy’s Chancery building 7 Lang Ha Street in Ba Dinh District, Hanoi, and uses a beta attenuation measurement principle to provide hourly PM2.5 concentrations in micrograms per cubic meter.
  • The hourly PM2.5 concentrations are converted into the U.S. EPA’s Air Quality Index (AQI) made available to the public on the www.airnow.gov website.
  • The instrument is operated and maintained according to manufacturer specifications, as well as following the U.S. Environmental Protection Agency’s Ambient Air Quality Surveillance requirements.
  • The instrument was sited using the U.S. EPA’s Probe and Monitoring Path Siting Criteria for Ambient Air Quality Monitoring, which includes important factors such as spacing from trees and other emission sources that can impact the readings.
  • Multiple U.S. embassies and consulates around the world have air quality monitors. Each such monitor follows the same guidelines in terms of siting, installation, operations, maintenance, and assurance of data quality. These guidelines also apply to all air quality monitors in the United States that are used to determine compliance with U.S. air quality standards.
  • The U.S. EPA has developed a formula to convert PM 2.5 readings into an air quality index (AQI) value that can help inform health-related decisions. Meanings of AQI numerical values can be seen in the chart below.  Please note that the U.S. EPA’s AQI includes air pollution in the form of both gases and particles, but U.S. embassies use particle pollution as an overall indicator for air quality.  For more information on AQI and how it is calculated, please click here.

Please click here for the Fact Sheet on Air Quality Monitoring.

Air Quality Index Levels of Health Concern Numerical Value Meaning
Good 0 to 50 Air quality is considered satisfactory, and air pollution poses little or no risk
Moderate 51 to 100 Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution.
Unhealthy for Sensitive Groups 101 to 150 Members of sensitive groups may experience health effects. The general public is not likely to be affected.
Unhealthy 151 to 200 Everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects.
Very Unhealthy 201 to 300 Health warnings of emergency conditions. The entire population is more likely to be affected.
Hazardous 301 to 500 Health alert: everyone may experience more serious health effects