Building Services Engineering 5th Edition Handbook

160 Ventilation and air conditioning
particles and vapours plus other contributory factors:
• tobacco smoke
• body odour
• deodorants
• vapours from cleaning fluids, photocopiers, paints and furnishings
• dust
• bacteria
• noise
• flickering lamps
• glare from artificial illumination and the sun
• carpets
• polyvinyl chloride (PVC)
• paper
• formaldehyde
• volatile chemicals
• bacteria grown in stagnant water in humidifiers
• treated water aerosols distributed from showers, washing facilities or fountains
• open-plan office
• too many people.
The air temperature, humidity and air movement, which will seem either stagnant or too
draughty, can rarely please more than 95% of the occupants and frequently please a lot fewer.
The total environmental loading upon the occupants may rise to an unacceptable level, which
can be low for those who are hypersensitive, that is, physically and psychologically unable to
fight off such a bombardment of additional foreign agents to the body.
Sick building syndrome, SBS, is epitomized by the occupants’ exhibiting a pattern of lethargy,
headaches, dry eyes, eye strain, aching muscles, upper respiratory infections, catarrh and aggravated
breathing problems such as asthma, upon returning to their workplace after the weekend.
Apparent causes are sealed windows, air conditioning, recirculated air, recirculating water humidifiers,
high-density occupation, low negative ion content, smoking, air-ductwork corrosion,
airborne micro-organisms, dust, and excrement from dust mites in carpets. SBS can be defined
as a combination of health malfunctions that noticeably affect more than 5% of the building’s
population.
This means that there should be sick house syndrome as well. Perhaps there is, or perhaps we
are more tolerant at home. Cases of formaldehyde vapour irritation after cavity insulation have
been noted. The pattern of house occupation is different, and variation of climatic controls is
easily achieved.
Relief can be gained by operating windows, temperature control, sun blinds, air grilles, by a
brisk walk or by going outdoors to stimulate the body to sweat toxins out.
It has been easy to blame air conditioning for SBS, but the cause is more complex and has
much to do with the standards we demand of our buildings, the psychological influence of having
to go into the workplace at all and the total internal environment created. Naturally ventilated
buildings often have a higher bacteria and dust count than air-conditioned buildings, which use
filters and have sealed windows.
Outbreaks of Legionella diseases have been attributed to the growth of bacteria in stagnant
water in wet cooling towers. These bacteria are distributed on air currents and breathed in by
those susceptible to infection, sometimes with fatal results. Dry heat exchangers are preferred
for discharging surplus building heat gains back into the external atmosphere but they are rather
large. Adequate cleanliness and biocide dosing of recirculated cooling-tower water is mandatory.