ASHRAE, Indoor Air Quality, Radiant Cooling

How Is Indoor Air Quality Standard Regulated In Existing International Codes?

People spend upwards of 90 % of their time indoors. That makes the indoor environment crucial to regulate carefully. This has various components, but none are as important as the quality of the air.

China Air Quality

Studies have shown that proper regulation of indoor air quality standard (IAQ) lowers the microbial load in the air (reducing allergic reactions, and risk of disease), removes severe health hazards from poisoning by pollutants (such as radon, carbon monoxide, smoke, volatile organic compounds, etc.) improves comfort and performance, and reduces absenteeism, among other things. The monetary benefits of regulating IAQ standard alone has been estimated to be in the tens of billions of dollars each year.

Clearly, for health and financial reasons, governments should be motivated to deal with IAQ standard, which raises the question: How is Indoor Air Quality standard regulated in existing international codes?

Unfortunately, there is no easy, short answer to this question. This is partly because the focus on IAQ standard in building codes is fairly recent. For example, the Ministry of Health in China only instituted hygiene standards to regulate indoor air pollution in 1988, the code used in North America to regulate IAQ, the American Society of Heating, Refrigerating and Air-Conditioning (ASHRAE) Standard 62.1, was first commissioned in 1997, and Australia only published their first document to regulate IAQ, the National Construction Code (NCC), in 2016! As such, there has been little time since the conception of IAQ standards to develop comprehensive, international codes. This has not been helped by the fact that innovation in IAQ standards necessarily needs to trail behind the medical evidence for the need to actually regulate IAQ at all.

Accumulatively, this has led to a lack of international consensus on IAQ standards, and to the international codes that do exist being complex, non-uniform, and often not bound by any laws to mandate their implementation. This problem was recently highlighted by a report prepared for the Asia-Pacific Economic Cooperation (APEC) organization, which found that out of 21 countries, only seven had mandatory regulations pertaining to IAQ, five showed minimum requirements for addressing IAQ, and nine did not address IAQ standards in their legislation at all (Chong, 2013).

Obviously, this has been identified as a problem. Two publications in particular that epitomize the concern over a lack of IAQ standards being represented in international building codes are the books, Air Quality Guidelines for Europe (first edition published in 1987, second edition in 2000) by the World Health Organization (WHO), and, Indoor Air Quality Guide: Best practices for design, construction and commissioning (published in 2009) by ASHRAE. In response, several organizations have done considerable work developing internationally applicable IAQ standards, including ASHRAE, the International Organization for Standardization (ISO), the European Committee for Standardization (CEN), and the Leadership in Energy and Environmental Design (LEED). Also, many countries have developed independent legislation for the regulation of IAQ standard. A discussion of all of these would be ideal. However, I will only briefly discuss the IAQ standard codes in China’s legislation, as these are used across most of Asia, as well as the most widely used code for IAQ standard, ASHRAE Standard 62.1.




In China, legislation for buildings is a compilation of a large number of ‘GB standards,’ generally organized into codes. There are over 21 400 of these GB standards, of which approximately 15 % are mandatory, with the rest voluntary, as denoted by a prefix code (GB/T indicates voluntary national standards, and GB/Z indicates national guiding technical documents). In 2002, China issued several of these standards to regulate IAQ in residential apartments and office buildings. A directive called the “Hygienic Norm of Indoor Air Quality” included many of these. This covered the concentration of pollutants in the air (Table 1), concentration of radon (200 – 400 Bq/m3 equilibrium equivalent concentration, yearly average), relative humidity (30 – 60 % in winter, 40 – 80 % in summer), and the ventilation rate (< 0.3 m.s-1).

Table 1: Concentration limits for indoor air pollutants in China’s “Hygienic Norm of Indoor Air Quality” directive. From Bai, Z., Jia, C., Zhu, T. & Zhang, J. (2002) Indoor air quality related standards in China. Proceedings (IV) of indoor air, 1012-1017.

Concentration limits for indoor air pollutants in China



ASHRAE Standard 62.1: Ventilation for Acceptable Indoor Air Quality’ is considered one of the most progressive inclusive standards of IAQ. It covers a comprehensive list of factors that affect IAQ, including moisture and dirt in heating ventilation and air conditioning (HVAC) systems, relative humidity levels (< 65 %), maintenance of HVAC systems, outdoor air quality requirements (air may be mandated to pass through a MERV 6 or 11 filtration unit, and intake air ducts have mandated distances from sources of air pollution), concentration of pollutants (Table B-2, ASHRAE Standard 62.1), envelope tightness, and ventilation rates (either per-person – dependent on the number of people within the space, or per-unit-area – dependent on the rate of contaminants released into the air by materials not related to the number of occupants).

Ventilation is the main focus of ASHRAE Standard 62.1, with a number of equations to calculate various components of ventilation, including outdoor zone airflow, zone air distribution effectiveness, and system ventilation efficiency. In addition to a multitude of equations, the required rates are specifically stipulated for almost every conceivable location, from prison cells, coffee stations and bedrooms, all the way to lecture halls, museums and courtrooms (Table 6-1, ASHRAE Standard 62.1). This deals mostly with comfort levels, with higher ventilation rates corresponding to lower levels of dissatisfaction (Figure 1). This is one aspect of ASHRAE Standard 62.1 that is reflected in most codes on IAQ; ventilation is the most common factor to appear in legislation for IAQ standard worldwide (Olesen, 2004). In fact, often IAQ standards are just a requirement for a particular ventilation rate. However, once again this is subject to a lack of consistency internationally. For example, some European countries (such as Denmark and Sweden) have mandated ventilation rates similar to ASHRAE Standard 62.1, while others (such as Germany, Italy, and all the countries in the United Kingdom) only have recommended minimum rates.

percentage of people that are dissatisfied by their perceived IAQ

Figure 1. The percentage of people that are dissatisfied by their perceived IAQ as a function of the ventilation rate. From Olesen, B.W. (2004) International standards for the indoor environment. Indoor Air, 14, 18-26.

The major drawback of ASHRAE Standard 62.1 is in the definition acceptable IAQ, “air in which there are no known contaminants at harmful concentrations as determined by cognizant authorities and with which a substantial majority (80% or more) of the people exposed do not express dissatisfaction.” This definition leads the standard to have objectives designed more to enhance comfort than health.



There is a vast amount of work and research going into the development of international codes for the regulation of IAQ standard. The last two decades have seen substantial revisions to existing codes, as well as the introduction of a wealth of new guidelines. Two of the most influential codes have been briefly discussed here; the vast set of standards used in China, and ASHRAE Standard 62.1. In their current form, these standards cover many aspects of IAQ, and their policies are incorporated into the building codes used in countries around the world. However, despite the fact that they are considered relatively comprehensive, they are still intentionally a collection of minimum requirements. Moreover, many of the stipulations are voluntary. This leaves the potential for existing codes for IAQ standard to remain inadequate, or even outright ignored.

The good news is that there are now extensive guidelines on IAQ regulation, and a growing effort worldwide to incorporate mandatory IAQ standards into legislation. This has prompted international codes on IAQ standard to be more than simply consensus, minimum requirements for ventilation. Existing codes now include recommendations on all three of the factors that can control IAQ; ventilation, source control, and filtration and air cleaning.


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