States that an air filter can prevent sources of infection entering the ventilation system. It keeps the ventilation system in good condition, and maintains the air flow rate, the temperature and the RH for which is has been designed. It also keeps the efficiency of the heat exchangers at a high level. The same areas of attention should apply to both the return system and the supply system.
The modern era of tuberculosis began in the mid 1980s. At that time it was realised that tuberculosis had not only ceased to decline in many developed countries, notably the USA, but was actually increasing. This forced health services to look more closely at the problem of tuberculosis. It was realised that the disease was out of control across most of the poorest regions of the world, especially Central Africa and South Asia. It was for this reason that in 1993 the WHO took the unique step of declaring tuberculosis to be a world emergency.
According to published statistical data, most TB contamination occurs from unknown and unsuspected TB carriers. It can be found in many areas of a health care facility where, based on the building code requirements, the air is not exhausted to the outside but recirculated to other areas of the facility. Although any system exhausting instead of recirculating the air greatly minimizes the risk of contamination, all-exhaust systems are not used because of their increased energy consumption. As an alternative method, recirculated air is HEPA filtered.
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