Mike Sopp looks at the findings of the latest survey into the impacts of poor indoor air quality, the relevant legal requirements and best practice with regard to improving it.


In June 2016, the Building Engineering Services Association (BESA) published the findings of a survey they completed in relation to indoor air quality in the workplace.

According to BESA, almost 70% of those office workers asked, “believed poor air quality in their place of work is having a negative effect on their day-to-day productivity and well-being” and a third are “concerned that poor indoor air quality could be having a negative effect on their health”.

As a result, BESA is now working with other leading industry bodies to raise awareness of the impacts of poor air quality and how those with responsibility for the workplace can achieve good air quality.

Impacts of poor indoor air quality

The Chartered Institution of Building Services Engineers (CIBSE) suggests that good indoor air quality can be defined as “air with no known contaminants at harmful concentrations”.

The source of contamination can be from both outdoors, and inside the workplace. External pollutant sources include vehicle exhausts, discharges from combustion appliances, industrial processes, etc. Fungal spores and pollen from vegetation may also cause air pollution problems.

Internal pollutant sources include burning fuels, emissions from building materials, furnishings, cleaning products, electrical equipment, etc.

In terms of actual types of pollutants and their associated risks, the most common are:

  • volatile organic compounds that may cause respiratory problems

  • particulate matter such as dusts and fibres that may also cause respiratory problems

  • gases, in particular carbon monoxide and dioxide leading to oxygen deprivation

  • biological particulates such as fungi, mould and dust mites that may cause breathing difficulties

  • radon that may cause lung cancer (responsible for over 1,000 deaths annually).

Therefore, building occupants may be exposed to a mixture of various airborne contaminants. Any potential health hazards will be dependent upon the pollutants toxicity, concentration and exposure period. Health issues range from nuisance (eg bad odours), to irritation (eg headaches and coughs) to serious toxic effects including infections and life-threatening illness.

Sick Building Syndrome is a term often used to describe many health effects or conditions suffered by occupiers with symptoms including headaches, eye strain and lung irritation. Of interest, the BESA survey found that two-fifths of respondents believe that poor air quality is linked to many of these symptoms and that:

  • two-thirds of workers experience fatigue and lapses in concentration

  • two-fifths of workers experience watery or irritated eyes on a frequent basis.

With office workers spending up to 90% of their work day indoors, the need to achieve good indoor air quality is crucial.

Legal requirements

Ventilation is a central component for good indoor air quality. From a legal perspective the Building Regulations (Part F) specifies adequate fresh air rates and sets performance criteria for several air pollutants including VOC’s and carbon monoxide.

The Workplace (Health, Safety and Welfare) Regulations requires effective and suitable provision to be made to “ensure that every enclosed workplace is ventilated by a sufficient quantity of fresh or purified air”.

Taking into account the above, the key to achieving good indoor air quality is therefore based upon:

  • the provision of sufficient fresh air supply rates to dilute and remove pollutants

  • effective ventilation in a form that will most efficiently remove pollutants

  • low pollutant emission rates from internal sources

  • low external pollution concentrations entering the property.

According to CIBSE, the amount of ventilation required for air quality depends on occupant density, their activities and pollutant emissions within a space. However, in general terms fresh air supply rates should be a minimum of 10 litres per second per person.

In addition to ventilation requirements, consideration should be given to how internal pollutant emissions can be eliminated, reduced or segregated from occupiers. Some of the more common pollutants may have occupational exposure limits that under the Control of Substances Hazardous to Health Regulations must be identified and risk assessed.

It is also worth noting that suppliers of certain products should be meeting all necessary requirements to reduce emissions, for example from flooring materials.

The Health and Safety Executive Approved Code of Practice L24 states that “air which is taken from outside can normally be considered to be fresh”. However, CIBSE state that “it cannot be assumed that outside air is fresh and free from pollutants”.

The level and type of outdoor pollutants entering the building will depend upon a number of factors such as location of the building (eg proximity to high traffic volumes or industrial processes), type of ventilation system utilised and associated filtration elements and if intakes are located close to exhausts from other systems.

Clearly, eliminating or reducing these pollutants at source is mostly out of the control of the building occupier but they will need to be taken into account when determining if indoor air quality is adequate.

Standards and good practice

For those with responsibility for achieving good indoor air quality, the challenge is determining whether this is being achieved and if not, what more can be done to meet this requirement.

There are a number of inputs to this process. An initial study can be completed to ascertain if occupiers are satisfied with the air quality. This could be through the completion of a questionnaire by occupiers along with a review of any previous issues or concerns raised by occupiers.

Clearly, some form of benchmark is required to determine if there is an issue. CIBSE suggest that indoor air quality may be said to be acceptable if:

  • not more than 50% of the occupants can detect any odour

  • not more than 20% experience discomfort

  • not more than 10% suffer from mucosal irritation

  • not more than 5% experience annoyance, for less than 2% of the time.

Where the above threshold limits are exceeded, it may be necessary to undertake more detailed investigations. This could include:

  • surveying the property to identify potential sources of internal emissions

  • undertaking measurements to determine concentrations of pollutants

  • surveying the external perimeter of the property to identify external pollutant sources and means of entry

  • Reviewing any mechanical ventilation systems in terms of design, installation and maintenance.

In addition to the above, consideration may be given to the location of particularly vulnerable individuals (eg those with underlying respiratory issues) and sources of pollutants.

In terms of taking action, this will be influenced by the outcomes of any investigation and subsequent risk analysis. As with any issue, the employer must do what is reasonable. This may include, for example:

  • replacing certain materials by equivalent items with lower emission rates

  • ensuring that air intakes are not adjacent to local outdoor pollutant sources

  • using appropriate filters in any mechanical ventilation system

  • ensuring mechanical ventilation systems are well maintained to best practice

  • increasing fresh air flow rates (but ensuring this itself does not create thermal discomfort)

  • using “green screens” externally to reduce pollutants between roads/processes and air intakes.

There are numerous guides and standards produced by various professional bodies in relation to indoor air quality.

Going forward, due to the wide concerns over air quality being expressed by various professional bodies, BESA is now working with other organisations including CIBSE to raise awareness of air quality issues. It is also pushing for indoor air quality to be included in the proposed revised Clean Air Act.

BESA is also aiming to produce an IAQ Standard, stating that its aim and purpose will be to create “safe havens” from pollution indoors and enable statutory annual IAQ inspections to be undertaken. The standard is expected to be published some time in 2018/19.

Further information

Building Engineering Services Association www.thebesa.com

Chartered Institution of Building Services Engineers www.cibse.org:

  • KS17: Indoor Air Quality and Ventilation

  • TM21: Minimising Pollution at Air Intakes

  • TM40: Health Issues in Building Services

  • Guide A: Environmental Design

BSRIA: www.bsria.co.uk:

  • At a glance — Indoor Air Quality

Last reviewed 12 September 2017