Air Quality Guidelines

Air Quality Guidelines


The safety of our students and the OCACW community as a whole is paramount, and the current air quality in Wuxi sometimes necessitates us to carefully define the guidelines under which we operate. OCACW strives to provide the safest environment feasible, and this document clarifies the steps and procedures taken to achieve this goal.

Air Quality

In order to understand the guidelines fully, it is critical to understand what we mean by “air quality” and how it is measured. As different countries and agencies use different guidelines, users must consider the data source and how it is derived for it to be interpreted accurately and with validity. A summary of the data terminology and sources of information used at OCACW is located in Appendix 1 and should be read to gain a full understanding of what different readings mean.

Air Quality Monitoring and Preventative Action Procedures at OCACW


  1. The school nurse will monitor the AQI throughout the day and report readings to relevant personnel as per the procedures laid out for each level in the “Air Quality Index with Measures to be Taken” chart below.
  2. The AQI readings for internal events will be taken from our closest monitoring site. US Embassy readings will also be monitored by the school nurse and the Administration and may be used instead on a case-by-case basis, if there is a large discrepancy giving cause to question the validity of other readings.
  3. An alert email with a copy of the “Measures to be Taken” chart will be sent by the school nurse to the following staff when AQI levels exceed 150, alerting them to the need to begin appropriate protocol steps depending on the level. Administration members and faculty with mobile phones continually receive WeChat messages, and will follow-up with faculty who are teaching or on duty and not in a position to receive the alert for action.
  4. Once an alert email has been sent, updated readings will be emailed at the following times to the designated personnel until the readings drops below 150: 10:30am; 11:45am; 12:50am; 3:10pm. If the official release of AQI readings is delayed, then these alert emails will be delayed as well.
  5. The school nurse will notify teachers of students with identified respiratory problems, so as to be aware of individual limits to observe if the AQI goes above the student's tolerance level.
  6. If school is cancelled due to OCACW red code measures (reference table below), the General Manager will activate the Emergency system to notify parents with an email, as well as post a notice on the school website.
  7. Updates will be sent via email and posted on the school website as needed.

Air Quality Index with Measures to Be Taken at OCACW

Air Quality Index with Measures to Be Taken at OCACW

Outside of school / after school

  1. An admin staff member will be designated to monitor and inform the supervising teachers of the air quality when on a fieldtrip or camp, and preventative measures applicable to the alert level will be taken when the AQI goes over the set limits. The designated monitor will be identified in the risk assessment matrix for fieldtrips, and must ensure they have the means to access AQI readings during the fieldtrip.
  2. For school fixtures outside of school time, the supervising teacher (CCA Coordinator, Athletic Director, or Event Coordinator) will designate someone to monitor the AQI, and instruct preventative action as per policy.


For school sports events, OCACW follows the standard AQI Response Protocols set by the International Schools Athletics Conference (ISAC):

ISAC recognizes that while many schools have varying approaches and rules pertaining to AQI, it is left to the host school and event director to determine whether an outdoor event can go ahead - based on the following ISAC agreements [using US Embassy AQI readings]:

  • An outdoor sports tournament should not begin when the AQI is 251 or above - with 06:15 notification from the event coordinator(s)
  • Any sports tournament that begins must be ended when the AQI (if able to be measured) moves to 276 or above during the event.
  • Final results of a shortened tournament should be determined by the event tournament coordinator, after consultation with participating coaches.
  • Individual schools will work through decision-making for league matches.

Air Purifier Use procedures

  1. The school nurse will email faculty to inform them to turn air purifiers on when the AQI goes over 51.
  2. Staff must shut the doors and windows of classroom when the air purifier is on, instruct students to keep them closed, and minimise their opening during air purifier use times.
  3. Air purifiers should be turned off after the AQI drops under 50 for 2 consecutive hours; or turned off immediately if the AQI drops to below 30.
  4. Teachers with students having identified respiratory problems may be instructed by the school nurse to adjust their on-off limits to protect such individuals.

Other considerations

  1. Parents who have children with identified respiratory problems are required to report the conditions to the school nurse and provide supporting documentation to enable specific steps to be taken to protect them.
  2. Parents are requested to supply high quality masks (PM2.5-proof masks designed for children), and ensure they bring it to school with them each day in case it is needed.
  3. OCACW takes all feasible precautions to protect our students when the air quality deteriorates. Parental requests for individual precautionary measures will be considered on a case-by-case needs basis and where feasible, the school will work with the parent to satisfy all reasonable requests. Impact on classes, faculty and individual students will be considered when such requests are made.
  4. Parents are requested to respect the school’s attendance policy and attempt alternative measures (such as masks) rather than withholding students from school if the AQI has not forced a school closure.
  5. In the event of a school closure, the Administration will consider the length of closure before making any decision on the need for make-up days. For any occasional 1-2-day closure, appropriate online work will be provided to students via digital learning platforms (ClassDojo, Managebac, etc.) to ensure continuance of learning.
  6. In the event of a school closure, academic staff are required to provide work for students from home but are not required to come in to school. Business admin staff are required to attend work as per usual.
  7. The following will not be cancelled due to pollution closures: a. IB exams
  8. SAT, ACT, IELTS, TOEFL and other standardised tests as/ if needed
  9. Mock/ Semester/ Final school exams
  10. Local/ Provincial/ national exams

(Note preventative measures will be taken on these days to ensure the safety of students, and students are advised to wear masks to and from school.)

  1. Supervision at home during a school closure is the responsibility of parents. An adult should be present to supervise young children at all times.
  2. In case of emergency, parents or students can contact their homeroom teacher for advice and/or assistance as the teachers will be checking student work online and will be available.
  3. OCACW intends to comply with all instructions issued by the District, City and/ or Province Education Bureaus, as well as the central Ministry of Education in the event a closure is advised for the protection of the students.

Information Sources & Further Reading:


  1. AQI Air Quality Index A Guide to Air Quality and Your Health
  2. AQI Basics
  3. AQI information in the US
  4. AQI Conversions in China
  5. WHO Air quality guidelines for particulate matter, ozone, nitrogen dioxide and sulfur dioxide
  6. Global update Summary of risk assessment
  7. Frequently Asked Questions (FAQs) on Haze (Ministry of Health, Singapore, Updated 28 June 2013)
  8. Air Quality Index – Wikipedia
  9. North Carolina: US EPA Office of Air Quality Planning and Standards, 2013 Revised Air Quality Standards For Particle Pollution And Updates To The Air Quality Index (AQI)

Appendix 1: AQI (Air Quality Index) Definition


“The AQI is an index for reporting daily air quality. It tells you how clean or polluted your air is, and what associated health effects might be a concern for you.” 1

AQI values are calculated for air pollutants using complex formula for each individual pollutant

  • The US Environmental Agency (EPA) calculate AQI for the 5 pollutants regulated by the Clean Air Act: ground-level ozone, particle pollution (also known as particulate matter), carbon monoxide, sulphur dioxide, and nitrogen dioxide.
  • China's Ministry of Environmental Protection (MEP) calculate AQI levels for 6 atmospheric pollutants: sulphur dioxide, nitrogen dioxide, PM10 (suspended particulates smaller than 10 μm in aerodynamic diameter), PM2.5 (suspended particulates smaller than 2.5μm in aerodynamic diameter), carbon monoxide, and ozone
  • To convert from concentration to AQI this equation is used: OCAC-AQI

I = the (Air Quality) index, C = the pollutant concentration,
Clow= the concentration breakpoint that is ≤ C, Chigh = the concentration breakpoint that is ≥C,
Ilow= the index breakpoint corresponding to Clow, Ihigh= the index breakpoint corresponding to Chigh
*The EPA have established 24-hour average breakpoints of fine particles for the equation

  • For each of these pollutants, established air quality standards are used to provide a scale highlighting implications to health. An AQI value of 100 generally corresponds to the accepted standard for the pollutant. When AQI values are above 100, air quality is considered to be unhealthy - at first for certain sensitive groups of people, then for everyone as AQI values get higher
  • The scale for each pollutant is non-linear (so an AQI of 100 does not mean it is twice the pollution of an AQI of 50, nor does it mean it is twice as harmful)
  • Comparisons between readings from different sources need to be considered carefully to be valid.
  • In China, multiple pollutants are measured at monitoring sites, and the MEP report the largest or "dominant" AQI value for the location. The US Embassy and Consulates only calculate AQI for PM2.5
  • In China, 24-hour breakpoints are used in the calculation of the AQI (as do the EPA in the US); the US Embassy and Consulates back-project real-time readings for 24 hours for the equation breakpoints (effectively making the resultant AQI more reactive)
  • Different monitoring agencies report differing AQI levels depending on where they get their data, and what formula they use to calculate AQI from the concentration of the pollutant.

At OCACW, we consider three data sets: The US Embassy readings, the local Environmental Monitoring  Centre  readings,  and  the  China  Ministry  of Environmental Protection readings as/if applicable.

  • Note different apps and websites publish AQI from different sources, so expect AQI readings from the same location to be different at times (most apps use the China MEP data rather than the BMEMC data as they report country-wide, as well as the US Embassy data which is calculated differently)
  • OCACW uses the BMEMC data in the first instance when acting upon levels, as it is deemed to generally be the most accurate.
  • The purpose of the AQI is to provide a simple method to help us understand what air quality means to our health. A six-level colour code is used to divide levels of health concern:

Air Quality Index Scale (US and China)

Air Quality Index Scale - OCAC

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