Guest blog by Sharon Isaac-Upton and Giulia Villanucci
Clean indoor air is essential for our health and wellbeing, offering relief to asthma and allergy sufferers and reducing disease transmission. This is especially important in clinical rooms with no windows and limited airflow. HEPA (High Efficiency Particle Air) filtration in healthcare facilities can significantly reduce the risk of cross-contamination, infections, and allergens, helping to improve patient outcomes. HEPA filters, developed in the 1940s, are highly effective at capturing particles in the filter’s fibres like viruses, moulds, and bacteria, even those less than 0.3 microns (ref. EN1822 Part 1 and ISO29463). However, clean air is not just about particle filtration. Maintaining well-ventilated spaces by opening doors between patients has a positive impact on mental health and helps disperse accumulated CO2, reducing feelings of stuffiness and drowsiness. Ventilation and filtration work hand in hand to ensure good indoor air quality.
Do I have natural or mechanical ventilation in my clinic?
Ventilation is the process of providing outdoor (fresh) air to occupants within a building and removing stale air that may be contaminated. Ventilation is essential for a healthy indoor environment and is widely recognised as a key mechanism for controlling the transmission of airborne infections. Ventilation can be provided through a number of processes, including mechanical ventilation using fans and ducts, natural ventilation which relies on passive flow through openings (doors, windows, vents), or a combination of the two. You should always identify what type of ventilation system you have. For buildings with poor ventilation, i.e. low fresh air supply rates, then portable air cleaners can play a role in controlling airborne particulate contaminants, including filtering out the smaller particles such as viruses, moulds, and bacteria.
What are the ventilation guidelines for healthcare premises?
The NHS Health Technical Memorandum 03-01 provides ventilation guidance for healthcare premises for new buildings and major refurbishments. This specifies a minimum of 10 air changes per hour (ACH) for treatment rooms. One ACH occurs when a volume of air delivered is equal to the volume of the room. If your ventilation system cannot achieve 10 ACH (it will not in the majority of cases and definitely not in the case of natural ventilation), then it is an option to make up the balance with portable air cleaners. However, it should be noted that a portable air cleaner does not introduce fresh air, rather it removes the particles from the air before returning the cleaned air into the room. This may be termed the ‘effective’ ventilation rate which could be expressed as the ‘effective air changes per hour.’
How can I introduce air filtration into my clinic?
A low-cost air filtration option is a Portable Air Cleaner (PAC) which cleans the air and therefore increases the ‘effective’ ventilation rate. The efficiency of a portable air cleaner is measured by its ‘clean air delivery rate’ or CADR but be mindful that most will show the top speed CADR only and this could be too noisy for clinics. To work out the minimum CADR your air cleaner needs, multiply your room volume by the ACH you want to achieve:
Room volume x ACH = CADR
For a typical health clinic, we will show you how to calculate an ‘effective’ ventilation rate.
- A clinic that measures 3m x 3.5m with a ceiling height of 2.4m has a room volume of 25.2m3
- Multiply this by 10 (ACH) to get a CADR of 252m3/hr
- This means to achieve an ’effective’ ventilation rate of 10 ACH, you should be looking at a portable air cleaner that delivers at least 252m3/hr at noise levels of less than 50 dB(A)
For the example of 10 ACH, this suggests that the air in the room is completely exchanged (cleaned) in just 6 minutes. However, in practice there is a gradual dilution effect that means in reality it will take longer to clean all the air in the room. If your ventilation system has a poor fresh air ventilation rate, and it cannot be easily improved, then a portable air cleaner could be a satisfactory solution. Select one with the highest CADR with the lowest noise levels. No additional technical features are needed for a HEPA air cleaner to work efficiently. All that is required is the combination of a powerful fan and a HEPA filter, classified as H13 or H14, which will allow the machine to operate efficiently and quietly. In fact, adding things like an ioniser has been proven to be detrimental to our health[1], while adding an Ultraviolet lamp inside a HEPA air cleaner is unnecessary when the HEPA filter is doing all the work[2] [3]
One final thought – there is no such thing as a medical-grade air cleaner, it is simply a marketing strategy when referring to HEPA H13 or H14 filters!
Further reading:
https://time.com/6143799/covid-19-indoor-air-cleaning/
https://itsairborne.com/clearing-the-air-on-air-changes-per-hour-time-to-move-on-cc95c0ec2cbc
British Standards Institute, 2019. BS EN 1822-1. High efficiency air filters (EPA, HEPA and ULPA) – Part 1: Classification, Performance testing, marking. London: British Standards Institute.
British Standards Institute, 2018 (1). BS EN ISO 29463. High-efficiency filters and filter media for removing particles in air. Parts 1 – 5. London: British Standards Institute
Sharon Isaac-Upton is Head of UK Operations at Smart Air UK. Giulia Villanucci is B2B Sales & Outreach Manager at Smart Air UK.
[1] https://www.england.nhs.uk/long-read/application-of-hepa-filter-devices-for-air-cleaning-in-healthcare-spaces-guidance-and-standards/ (section 2.2, second paragraph);
[2] https://www.texairfilters.com/researchers-confirm-some-air-cleaners-generate-ultrafine-particles-2/
[3] https://www.england.nhs.uk/long-read/application-of-hepa-filter-devices-for-air-cleaning-in-healthcare-spaces-guidance-and-standards/ (section 2.2 on UV), this not a requirement and it states that HEPA only is used for the capturing of bacteria. Position of UV lamp is mentioned and also note that the UV light is not designed to go on the frame, and it is the frame that will be handled. This means that care must be taken regardless to whether UV is there or not