HVAC sector has noted that authorities have looked to simplify guidance about measuring the gas as a means to identify poor ventilation rates and where improvements are needed

The Health and Safety Executive (HSE) has updated it guidance on measuring and managing ventilation rates to address the risk of airborne exposure to Covid and other contaminants.

These updates include an effort to simplify guidance on the use of CO2 monitors as a means to identify poor ventilation rates, as well as outlining options on the best means of balancing more passive measures such as window opening during winter months.

ACRIB, a UK-based umbrella body representing the heat pump, air conditioning and refrigeration sectors, said the revised guidance was based on feedback from businesses amidst concern about Covid infection rates.

The UK Government has recently moved to introduce some new restrictions to try and tackle the possible spread of the recently discovered Omicron variant of Covid-19 in the UK over concerns about a higher transmission rate than previously discovered strains. This could also increase scrutiny on the flow of external air into and out of buildings to limit build up of coronavirus.

CO2 monitoring

Among the main features of the latest HSE guidance are details of the types of monitors that should be used to measure CO2 and the types of buildings that may be suitable for using these technologies, ACRIB stated.

CO2 is not in itself a measure of coronavirus itself. However, build up of the gas, which is breathed out by people, can indicate that there is a need to improve ventilation and air flow rates in a certain space, the HSE stated.

According to the guidance, non-dispersive infrared (NDIR) CO2 monitors should be considered the most appropriate portable devise to current use in the workplace.

Due to the likelihood of CO2 levels varying across an indoor environment, monitors should be used at heat height and kept away from windows, doors or air supply openings.

The guidance has also noted the best options for making use of monitors in different sized environments. These range from smaller spaces of up to 50 square metres to larger areas over 320 square metres.

It is recommended that multiple monitors be considered in larger indoor spaces. However, these monitors are unlikely to give reliable measurements in larger spaces such as retail environments where the number of people present may change constantly over short periods of time, according to the HSE.

Window opening

ACRIB added that the HSE has also set out recommendations on opening windows as a means to better ventilate workplaces during the winter months when outdoor temperatures will be much lower.  It matches guidance that has previously been given to education providers that recommended opening windows in environments where there is insufficient or complete lack of mechanic ventilation. Some providers have raised concerns about the thermal comfort issues this creates.

The HSE backs partially opening windows and doors as one possible means to offer adequate ventilation. Where possible, higher-level windows should be opened, if at all possible, to create fewer direct draughts for occupants.


The HSE added, “If the area is cold, relax dress codes so people can wear extra layers and warmer clothing.”

An H&V News webinar looking at indoor air quality that was held last month saw experts warning that efforts to improve ventilation were being undermined by a lack of holistic understanding of different systems available to control air flow and how they can be used together.

Dr Vina Kukadia, an industry specialist from the University of Surrey’s Global Centre for Clean Air Research, said there was a critical shortfall in both research and understanding across the building engineering sector to understand the complex relationships between internal and external air quality.



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