Indoor Air Quality - Why monitor it?

20Apr / 2016

Indoor Air Quality – Why monitor it?

João Dyer, Senior Geo-Environmental Consultant at Ground-Gas Solutions (GGS), highlights the importance of monitoring indoor air quality and it’s effect on the working environment.


Why is monitoring indoor air quality important?

Maintaining good indoor air quality in a building is critical for ensuring a safe and comfortable working environment. Poor indoor air quality can lead to what is known as “sick building syndrome” or SBS[1], of which symptoms include loss of concentration, fatigue, headaches, breathing difficulties and nausea. This can lead to lack of productivity and even lead to staff having to take time off to recover, especially those with existing medical conditions such as asthma.


What are the causes of poor indoor air quality?

Typical causes of poor indoor air quality include over-crowding, inadequate ventilation, contaminants originating from certain types of building materials, volatile organic compounds, particulate matter and radon. Each of these poses a different health risk.

In order to assess indoor air quality and determine whether or not there is a health risk requires monitoring and sampling. There are a variety of ways this can be done and determining the correct monitoring and sampling strategy is of upmost importance. Once the indoor air quality has been assessed the results can be compared against existing guidelines, such as the Health and Safety Executive EH40/2005 Workplace Exposure Limits. Appropriate measures can then be put in place to either maintain and/or improve the indoor air quality to a level that provides healthy working environment.


Who regulates indoor air quality standards?

UK and international thresholds and limits, particularly in the workplace, vary significantly. For example, the US Environmental Protection Agency and the US National Institute for Occupational Safety and Health have stated that peak carbon dioxide concentrations over 1,000ppm (0.1% v/v) are an indicator of poor air quality. Whereas the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 62-2001 set an indoor guideline for carbon dioxide at no greater than 700ppm (0.07% v/v) above outdoor air levels. Therefore, with current background atmospheric concentrations around 400ppm, if a building occupier is in a space that encounters levels greater than approximately 1,100ppm (0.1% v/v) they are likely to experience some of the symptoms associated with SBS.

JM - Graph

Graph 1: Time series data of continuous carbon dioxide monitoring within the office. Click to enlarge.


What actions can be taken to monitor indoor air quality in my building?

The graph above illustrates monitoring undertaken by GGS in an office building in Manchester. The occupiers of the building had been complaining about the indoor air quality and it was suspected that the ventilation system wasn’t adequate. The graph shows a week-long snapshot of the carbon dioxide concentrations within one of the building’s open plan offices (Photo 1). Although the carbon dioxide concentrations do not exceed the EH40/2005 guidelines for workplace exposure limits (5,000ppm), there are daily peaks in carbon dioxide concentrations between 1,100 and 1,400ppm during daytime working hours. The office was fully occupied by staff at this time, meaning that some staff may have experienced early symptoms of SBS during these periods.


The source of carbon dioxide was most likely from the occupiers of the building from the natural process of breathing. The building’s ventilation system however did not appear to be sufficiently circulating enough fresh air in order to maintain carbon dioxide concentration at a comfortable level.  Most importantly it was found that carbon dioxide concentrations were not returning to background atmospheric concentrations (c.400ppm) overnight.


What are the benefits of indoor air quality monitoring?

In this particular case, it was recommended that all practicable steps be made to improve indoor air quality.  These include improvements to the current air conditioning and/or heating system at the building. The monitoring and sampling strategy undertaken by GGS at the site ensured that the indoor air quality was assessed in an efficient, cost-effective manner which provided both cost and time savings to the client. Steps were then quickly taken to ensure that the building’s indoor air quality improved to provide the occupiers of the building a safe and comfortable working environment. This ultimately led to a reduction in staff sickness and an improvement in staff efficiency.

JM - Pick

Photo 1: Discreet and silent continuous carbon dioxide monitor deployed in an office.

Featured on p48 of Tomorrow’s Health and Safety magazine, November/December 2015.

[1] HSE (1995). How to deal with sick building syndrome (SBS), HSG132.