CO in the Built Environment

Carbon monoxide poisoning is a serious health risk associated with the built environment, and it is important to understand how building regulations, energy efficiency measures, and appliance safety play a role in preventing carbon monoxide poisoning.

The CO Research Trust considers this such a high priority that this was the primary focus of the 2023 CO Research Conference.

Proper planning, installation, maintenance, and compliance with regulations are essential to create safe indoor environments and minimize the risks associated with carbon monoxide exposure.

What is the Built Environment?

The built environment encompasses all man-made structures, including homes, workplaces, and public buildings. Carbon monoxide can be produced within the built environment through the incomplete combustion of fossil fuels such as natural gas, propane, oil, and wood.

It is important to consider the following aspects of the built environment concerning carbon monoxide poisoning.


Proper ventilation is crucial to ensure that carbon monoxide is effectively expelled from indoor spaces. Buildings should be designed and maintained with adequate ventilation systems to ensure air exchange and to minimise the build-up of carbon monoxide.


The location of fuel-burning appliances, such as gas stoves, water heaters, and fires, should be carefully planned to minimize the risk of carbon monoxide build-up. They should be installed according to the manufacturers' instructions, safety guidelines and regulations.

Flue and Chimney Maintenance

Proper maintenance of chimneys and flues is essential to ensure that carbon monoxide from combustion processes is safely vented to the outside. Blockages or leaks in these systems can lead to dangerous carbon monoxide levels indoors.

UK Housing Stock

The UK has some of the oldest housing stock in Europe. This is largely due to the legacy of dwellings built during the Industrial Revolution, which still form the backbone of our urban areas today.

Much of England's housing stock is owner-occupied and built before 1919.

The age of a building affects energy efficiency as building techniques and regulations have changed over time, alongside wear and tear.

In 2016 the CO Research Trust funded a research project by University College London (UCL) which looked at the determinants of carbon monoxide exposure in the English housing stock: Modelling current and possible future risks.

You can read more about the project here, and download the full report.

The research identified the following.

  • The majority of homes (85%) are still heated by gas-fired systems
  • Flats tend to use other fuel types (primarily for safety reasons)
  • Solid fuels are still used in some older homes
  • Rural locations tend to have more solid, oil and electric fuel types relative to cities
  • Central London has the highest percentage of community heating

The findings of the research included.

  • Cities in general - and London in particular - experience the highest levels of outdoor carbon monoxide exposure.
  • Dwelling type, main fuel type, floor area, and how well-ventilated a home acts as modifiers to carbon monoxide exposure from indoor sources, with bungalows, terraced homes, and flats estimated to have higher indoor levels.
  • Owner-occupied dwellings appear to have generally lower carbon monoxide exposures from indoor sources when compared to other tenure types.
  • Working extract fans significantly reduce carbon monoxide exposure if used during cooking.
  • Urban areas tend to have higher carbon monoxide exposures due to high outdoor levels and the prevalence of dwelling variants such as flats and terraces that are at elevated risk.
  • Although the modelled outdoor carbon monoxide concentrations do not have high enough resolution to consider street-level exposure, it is likely that small flats near busy roads may be at a particularly high risk.
  • Energy efficiency retrofits increase the number of dwellings in England and Wales that exceed EU recommended carbon monoxide exposures by around 15%. The largest increase is in urban areas.

The Housing Trilemma

On the 5th of July 2021 the Department of Housing, Communities and Local Government (DHCL) published the Building Safety Bill.

This draft Bill was considered the “next step in ground-breaking reforms to give residents and homeowners more rights, powers and protections”.

Most importantly, this was about making homes across the country safer.

While the dangers of outdoor air pollution have been well documented, the often-overlooked area of our environment is the indoor space. It’s imperative that we strengthen our understanding of the key risk factors and effects of poor air quality in our homes.

In 2016 the Royal College of Paediatrics and Child Health and the Royal College of Physicians estimated that indoor air pollution may have caused or contributed to 99,000 deaths annually across Europe.

When it comes to housing policy, the health effects of air quality have to be balanced with the seemingly conflicting priorities of affordability, housing access and environmental sustainability – three critical elements that can appear mutually exclusive.

The CO Research Trust has identified this as The Housing Trilemma. How do we balance safety and health, with affordability and access and while still focusing on environmental sustainability?

Read more about the Housing Trilemma in this article.