Understanding HSE Coronavirus Ventilation Recommendations for UK Businesses (Part. 1)

Understanding HSE Coronavirus Ventilation Recommendations for UK Businesses (Part. 1)

23 August 2021
coronavirus particles entering an air conditioner

The latest guidelines set out by the Health and Safety Executive (HSE) will help you assess the current ventilation, air quality and air conditioning risks from coronavirus present in your place of business, so that you can deal with them in a safe and efficient manner – making your workplace safe and productive again.

Coronavirus Ventilation: Overview

Current UK law states that employers much ensure there is sufficient ventilated or fresh air within indoor workplaces. In order to accomplish this, the HSE recommends:

  • Natural ventilation, where fresh air circulates in the indoor workplace through open doors and windows or vents.
  • Mechanical ventilation, where through a sophisticated setup, fans and ducts constantly draw in a desired amount of fresh air from outside and circulates it within the office or business facility.

With that said, it is also recommended that employers and business owners continue to take the regular precautions for protecting everyone against coronavirus, such as keeping the facility clean and encouraging everyone to wash or sanitise their hands frequently.

This article, the first from a series of two, gives some general guidelines as set out by the HSE, which will help your staff members:

  • Identify areas in the workplace where ventilation is generally poor or non-existent
  • Decide on the necessary steps to improve and maintain good ventilation
  • Assess and understand the risk of breathing in small coronavirus particles (referred to as aerosol transmission) in tight or enclosed areas

Why is ventilation so important, especially in a pandemic environment?

Through adequate ventilation, the number of coronavirus particles in the air can be effectively reduced, thus, reducing the risk of aerosol transmission.

Every time someone breathes in these small particles, the risk of aerosol transmission increases, especially if the person carrying it continues to stay in a tight or enclosed area for an extended period of time.

Therefore, the risk of contamination and infection is much greater in poorly ventilated areas. It must be kept in mind that even though proper ventilation can significantly reduce the risk of aerosol transmission, workers must continue to practice social distancing, wear masks, avoid unnecessary hand-to-surface contact and avoid shaking hands.

The ventilation in your work spaces is considered to be adequate in terms of minimising coronavirus aerosol transmission as long as:

  • The total number of occupants is in line with the occupancy limits set out by the building design or building regulation authority
  • A reasonable supply of fresh air is present to comply with the minimum building standard. It is best to seek the advice of a competent ventilation systems engineer in this regard, and in the meantime, you can operate your current ventilation system (if you have one) on the maximum available air flow rate, as a precaution.

How to assess the risk of aerosol transmission

‘Adequate ventilation’ may mean different things to different workplace owners, depending on the individual workplace setting.

For example, you may cut down the risk of aerosol transmission by:

  • Ensuring that infected workers or anyone exhibiting symptoms do not come to work
  • Providing ventilation for the time being via fresh air flow and circulation

Deciding what ‘adequate ventilation’ means to you is a part of risk assessment, which we’ll be discussing in part two of the article. Once you have completed this assessment, we’ll be sharing examples of how to improve ventilation in order to reduce transmission (also discussed in part two).

In addition, you need to ensure that any control measures identified during the risk assessment must take into account all the various public health regulations and SOPs, as well as the specific guidance meant for your region:

How to identify poorly ventilated areas

The main idea behind your risk assessment is to identify all the areas in your facility which are frequently occupied and generally do not have good ventilation, in your opinion or experience.

These areas are to be prioritised for immediate improvement in order to cut down the risk of aerosol transmission as much as possible.

Here are a few simple ways to identify areas with poor ventilation:

  • Observe the areas where your workers are most of the time and particularly where no mechanical ventilation system has been installed or there’s no natural ventilation and air flow, such as open doors and windows, and vents.
  • Check that if you do have mechanical systems installed, they provide outdoor air or temperature control, or preferably, both; because if a system is only recirculating air and not pulling in fresh air from the atmosphere, the area is going to see poor ventilation.
  • Identify areas which smell bad or feel stuffy.

Carbon Dioxide Monitors: The why and how

You’d be amazed so as to how much CO2 people exhale, especially in an enclosed area. This excess build-up of CO2 is one indication that your work areas need improved ventilation.

Even though measuring CO2 levels in your workplace is not by any means a direct indicator of how exposed or vulnerable everyone may be to coronavirus, checking them can definitely help you identify areas with poor ventilation to begin with.

Why CO2 measurements can help you take the necessary action

CO2 measurements should not be used as ‘safe thresholds’ but as a broad guide to assess ventilation in any given room. Here’s something you can use for quick reference:

Outdoor CO2 levels are typically around 400ppm (parts per million) – a consistent indoor value of 800ppm indicates that a space is reasonably well-ventilated.

On the other hand, an average reading of 1500ppm over the occupied period indicates poor ventilation and, therefore, warrants immediate action where readings are consistently registering above 1500ppm.

With that said, if there is continuous talking at high decibels, such as a busy sales or customer service floor, or where people are constantly getting up and sitting down, moving around frequently, etc., you need to provide sufficient ventilation so that CO2 levels are consistently below 800ppm.

How to take CO2 measurements – CO2 monitors

Since CO2 levels may vary in an indoor space, it’s best to place or install CO2 monitors at about head level and away from air supply openings, windows and doors, in order to have an accurate reading.

Additionally, monitors should also be positioned 50cm away from workers because CO2 levels hover around up to a certain distance after exhalation. Therefore, monitors that are placed too close will probably register an unusually high reading.

Plus, it’s worth noting that measurements taken during the day can vary, because you may have a different number of occupants, activities and ventilation rates throughout the day. Doors and windows being opened/closed can also affect the measurements.

If the measurements in an occupied workspace is very low – well below 400ppm – or unusually high – more than 1500ppm – then it’s quite possible that the monitors have been placed in the wrong spot, and that you need to move them to get more accurate and consistent readings, provided that all other factors are mostly constant – such as doors and windows not being opened, as well as the number of people and activities remaining largely the same throughout the day.

When using a CO2 monitor, we’d recommend against a ‘snapshot’ reading because they are not the most accurate. What you should do is take multiple measurements or readings throughout the day and then take out an average value for any given room.

It’s also a good idea to monitor throughout the year, because seasonal changes may affect worker behaviour, such as having more hot beverages, or talking less at certain times of the business year, and especially when doors and windows are open to let natural air in during the cooler months.

Keeping all this in mind, your CO2 readings should help you decide whether your workplace is adequately ventilated or not.

Tips on getting the most accurate CO2 readings

  • Calibrate your CO2 monitor according to the manufacturer’s instructions, such as the warm-up time required for the monitor to stabilise, before taking any measurements.
  • Understand how to correctly use the monitor, including the time it needs to measure an accurate reading. Again, refer to the manufacturer’s instructions.
  • Take several measurements in your most used workplace areas in order to find a suitable ‘sampling’ location. This will provide an accurate representative measurement for the respective spaces. In larger spaces, however, you will probably need more than one sampling.
  • Take your measurements at ‘important’ moments throughout the day (as discussed above) and for at least one full working day, which ensures that your readings will be based on regular use and occupancy.
  • Record not only the CO2 measurements, but also the number of total occupants, the type of ventilation system currently in place, and the date. All this information will help you use the CO2 records to determine if the said area has poor ventilation.

Are CO2 Monitors always effective?

Well, no – CO2 monitors aren’t that effective in spaces which rely on air cleaning units as these (by design) remove air contaminants such as coronavirus particles, but do not remove CO2.

Large, open spaces and those with higher ceilings, like warehouses and food production halls, where there’s no way to tell if the air is fully mixed – means that CO2 monitors will not truly be representative of the CO2 levels or level of ventilation, for that matter.

So, to sum it up, CO2 monitors are not very effective in less populated areas or where there are only 1-2 occupants – fitting rooms or very large offices, for example.

Stay tuned for part two of the article, which discusses more key points to consider when assessing the level of ventilation in your working spaces.