Hong Kongs new government headquarters costing $670 million was effected by a fatal bacterial disease causing many people to fall ill. The bacteria spread through tiny water droplets circulating in buildings,and was found in 11 locations in the complex,including the offices of the chief executive and the chiefs of seven departments,in addition to three food facilities.
The US Environmental Protection Agency has reported that sick buildings cause an estimated loss of $61 billion a year in employee absenteeism,medical costs,reduced productivity,and lower earnings.
The term sick building syndrome is used to describe the occurrence of acute health and comfort effects experienced by the building occupants.
Sick Building Syndrome (SBS) is due to poor indoor air quality (IAQ),which results in severe and recurring discomforts such as nausea,headaches,cold,dry mucous,eye,nose and throat irritation,drowsiness,fatigue,dry skin and respiration problems.
It leads to slow damage of the respiratory systems,leading to susceptibility to viral infections and asthma.
If 20-30 per cent of the people occupying the air-conditioned area have the above symptoms,then one needs to examine the air quality in the building.
QUALITY OF AIR
We inhale oxygen and exhale carbon dioxide. The outdoor air,which is taken by the airconditioning unit provides oxygen. As such the amount of outdoor air is highly significant for its intake increases the capacity of the airconditioning system.
In most cases the intake of outdoor air is compromised while airconditioning a room with many occupants. The argument is that increase in the intake of outdoor air increases the capital and operating costs. What the proponents of this argument do not realise is that the outdoor air is as important as aesthetics in a building. Occupants of a building cannot function effectively if its intake is deficient.
Reasons For Poor IAQ
Design & selection issues :
Inadequate quantity of outdoor air
Bad quality and contaminated outdoor air,which is nothing but the exhaust air drawn near the generator room,toilet or pantry,car park,change rooms,blue printing room,cooling towers etc.
Leakage of foul air into the return air space from adjacent areas through wall openings meant for passage of conduit,light fixtures etc.
Photocopying machines,ammonia-printing machines wrongly positioned.
Outdoor air intake with automotive and industrial emissions
High humidity inside the airconditioned area due to improper dehumidification.
Generation of odours inside the conditioned area such as tobacco smoke,pollen and spores from indoor plants
Mildew and mould spores from the damp corners or on false ceiling where there is water leakage from the air-conditioning units.
Spray/deodorants in the conditioned area,damp carpeting.
Dirty supply air ducts,false ceiling,return air spaces and filters.
Dirty water accumulation in the drain pans,air coolers and evaporative cooling plants.
Dirty cooling coils.
Virus,bacteria,fungus from the air handling unit drain pan.
Increasing the ventilation rates and air distribution is often a cost-effective means of reducing indoor pollutant levels. At a minimum,heating,ventilating,and air conditioning (HVAC) systems should be designed to meet ventilation standards in local building codes.
Air cleaning has some limitations,but it can be a useful addition to source control and ventilation. Air filters are only effective at removing some,not all,of the pollution. Education and communication are important parts of any air quality management programme. When everyone associated with the building,from occupants to maintenance,fully understands the issues and communicates with each other they can work more effectively together to prevent and solve problems.
Overall,maintaining balanced,proper airflow through routine maintenance is the most important factor to ensuring excellent indoor air quality,odour elimination and a healthy living environment.
The author is associated with the Indian Society of
Heating,Refrigerating and Airconditioning Engineers