HEALTHCARE VENTILATION
Diagram 1: Clean air flowing from an Air Sentry air purifier.
mental health settings now require 10 air changes / hour and the patient discharge rooms require 6 air changes / hour. General wards and waiting areas in hospitals are also being considered as areas where increased ventilation is being provided, with a minimum of 6 air changes / hour becoming the accepted norm, which is significantly greater than the CIBSE occupancy guidance levels. Where air-handling units are not supplying enough air, the room ventilation rate can be supplemented by opening windows and/or the provision of air scrubbers.
Air scrubbers/Air purifiers These units are often portable, and are generally about the size of a small under counter fridge. They contain HEPA filters capable of trapping particles down to 0.01 micron in size, as discussed in the NASA research into these filters in 2016.1 The deployment of these portable units can cause issues in large hospital Trusts, as many types need to be maintained
Diagram 2: Input air being drawn into an Air Sentry air purifier.
every two weeks – a task which tends to be delegated to the end-users. This equipment also needs to be asset tracked for its location, so that the Estates Department can check the units at least every three months. Some air purifiers are fitted with additional UV light units, which have been shown to remove viruses. Over time the recirculated air pulls dust and debris through the filters, degrading the performance of the unit. It is thus important that the filters are changed periodically, typically every six months, or whenever the filter becomes blocked. There is usually an indicator on the unit that shows when the filters are becoming blocked.
Potential air purifier issues Potential issues with air purifiers include failure to change the filters in a timely fashion, and not using the correct process for changing them – problems that can be mitigated by showing end-users how to manage the units, and also putting
information notices on the air purifiers to explain how to change the filters. The filter life is reduced if the unit is located in an area with high levels of airborne debris, for example near a busy entrance to an Accident and Emergency unit. As with any portable unit, there is a risk that the purifiers could be switched off by staff, and again this problem can be reduced by educating staff and possibly appointing air purifier ‘champions’ to monitor each unit and check it on a weekly basis. Andrew Carnegie, inventor of the Air Sentry air purification system, and managing director of Air Sentry, shared his thoughts on his product (see Figure 1) and how it can be used in healthcare environments. He said: “Our products are well-thought-through systems, designed for clinical use. Air Sentry systems use an ULPA-based filter which is down certificated to H14. This means that it can trap particles down to 0.007 micron, much smaller than a conventional HEPA filter. The arrestance (a measure of the ability
Figure 2: A large legacy belt-driven fan that could be replaced by a fan wall.
Figure 4: A heavily loaded duct. February 2022 Health Estate Journal 55
Image courtesy DRLC Ltd
Diagram courtesy of Air Sentry Ltd
Image courtesy DRLC Ltd
Diagram courtesy of Air Sentry Ltd
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68
