Everyone is familiar with air conditioning these days. Supermarkets, shopping centres, offices – even homes come equipped with centralised HVAC systems that regulate the interior temperature to keep it comfortable and pleasant all year round.
The Importance of Infection Control
Whenever large numbers of people congregate there is the potential for disease transmission. Hospitals are a unique breeding ground for disease and infection as they are one of the few places that large numbers of poorly people are brought together. Firstly, there are patients that have been admitted with complications due to disease or infection who can act as a source of bacteria and viruses. Secondly, there are those who have compromised immune systems, either because their immune system is damaged or because their treatment suppresses the activity of the immune response. This second category is especially vulnerable as their body no longer has the ability to protect itself from even usually mild infections. Thirdly, there is the workforce and general public. The sheer numbers of people entering hospitals daily mean that a certain proportion of them will be carrying infections – in some cases without symptoms – and will leave behind some of their germs through surface contact or by contaminating the air.
If you’ve visited a hospital recently you have probably been asked to use hand sanitising
gel – or to wash your hands thoroughly – especially before entering a ward or clinic area. This is to minimise the number of viruses and bacteria that you are bringing into the area with you. Staff will wash their hands frequently and you will see cleaners hard at work scrubbing and washing down surfaces. Materials, such as curtains and cubicle dividers are increasingly being made of disposable paper instead of germ-fostering fabric and bedding is kept to a minimum and made of fabrics able to resist sanitising during the laundry process.
All these precautions are to avoid the spread of disease through surface to patient or staff to patient contact. A whopping 1 in 25 patients will acquire an infection whist in hospital, not as a complication of their condition but from the environment in which they are being treated. Around 1 in 10 of these cases will result in early, and avoidable, death. Whilst hand-washing is a huge preventer of disease and infection transmission it is not the only vector through which patients become infected.
Infection control is a serious matter for hospitals. Many of the bacteria found are extremely nasty – Klebsiella spp., Staphylococcus aureus, Clostridium difficile, E. Coli, MRSA and gram-negative bacteria have all been found in hospitals. Several of these unpleasant organisms are now resistant to most antibiotics and the medicines required to treat them can have unpleasant side-effects. This can definitely be a case of the cure being as bad as the illness itself.
Hospital acquired infections are not only a serious matter from a clinical perspective. From an economic one the extra costs of longer hospital stays, medicines and nursing care all add up. For example, Kettering had an outbreak of MRSA that was estimated to have cost £400,000 to deal with, mostly due to the costs involved in setting up and staffing isolation wards for the affected patients. Some estimates put the national cost of dealing with hospital acquired infections at £1billion annually.
In the Air
It’s not just surface contamination that can spread diseases. Every time an infected person breathes they release germs into the air around them – and a cough or sneeze can transmit viruses and bacteria across a room. In fact, recent research from MIT shows that, under the right conditions a sneeze, can travel 200 feet. That could be the length of a hospital corridor.
And it is in removing airborne contagions that provides the role for air conditioning in infection control. The air needs to be filtered of large particles to protect the air flow within the air conditioning ducts and across the coils. To reduce the bacterial and viral load of the air being manipulated by the system a HEPA filter can be installed as well as the large particle dust filter. HEPA filters – High Efficiency Particulate Arrestance – remove around 99% of particles larger than 0.3microns. A MRSA bacterium, for comparison, is around 1 micron in size.
How air conditioning works
At the heart of the air conditioning system is a heat-exchanger. Warm air from the environment is blown across the coils to warm up the refrigerant inside the evaporator coils. A pump ensures that the refrigerant keeps moving through the system from the warm side to the cool side. On the cool side the refrigerant is compressed to release the stored heat and cooled by blowing air across the condenser coils. The air is filtered as it is extracted from the room and before passing over the coils to keep the interior of the air conditioning system clean and to avoid recycling contaminants.
By extracting the air efficiently and quickly the airborne pollutant load can be significantly reduced which in turn reduces the number of infections caused by simply being near an infected patient- even if no contact occurs.
Of course, it is vital that where air conditioning is fitted in hospitals it is serviced on a frequent schedule so that the dirty filters can be exchanged for clean ones to avoid the air conditioning system itself becoming a source of air contamination.
Protecting Air Quality
Hospitals are necessary to treat the sick, elderly and injured and it is important to keep patients safe whilst they are under their care. Whilst promoting hand hygiene and adopting procedures and policies to maximise the cleanliness of surfaces goes a long way towards creating a healing environment it is important to remember that many bacteria and viruses can survive in the air and thus air conditioning is an important weapon in the fight against hospital acquired infections.