Building Services Engineering 5th Edition Handbook

Ventilation and air conditioning 167
31. Why might an under floor air distribution system, UFAD, have benefits?
1. Keeps feet cool.
2. Quieter than ducts within ceiling.
3. Supply air within the floor void cools concrete floor slab thermal mass.
4. Keeps under floor power and communications cables cool.
5. There are no benefits as it costs more.
32. How could a chilled-water cooling coil distribute bacteria into occupied air-conditioned
rooms?
1. It cannot, as air temperature remains too cool.
2. It will not under normal operation.
3. Condensate water trap between drain tray and sewer always maintains a water seal.
4. Water seal in P-trap between drain tray and sewer may become dehydrated and allow
sewer gases to pass into the air-handling unit and supply duct.
5. It will not when adequately maintained in accordance with codes and standards.
33. How could a cooling-water tower become a health hazard?
1. It cannot while adequately maintained.
2. Very easily, bird droppings may create bacterial growth in cooling water immediately
after monthly servicing work and inspection.
3. Chemical dosing with biocide does not allow any cooling-tower water contamination.
4. Cooling tower is outdoors and so is no more a health hazard than an ornamental
fountain.
5. Cooling-tower water is always too cool to support growth of bacteria, mould or algae.
34. What can be done to maintain the health and safety of the internal surfaces of ducted
ventilation and air-conditioning systems?
1. Replace aged air ducts.
2. Increase air velocity to blow deposits out of ducts and terminal units outside of occupied
hours.
3. Change air filters regularly.
4. Internal visual inspection, compressed air brushing, scraping and vacuum cleaning.
5. Nothing more than maintaining air filters to keep air and ducts clean.
35. Where can sinusitis, asthma, pneumonia and skin dermatitis originate?
1. Mould spores in warm humid uncleaned air and water building services systems.
2. Contaminated outdoor air.
3. Low air humidity.
4. Contacting people with breathing infections.
5. Warm humid air in crowded buildings or transportation.
36. When carbon dioxide level in occupied rooms is sensed for control of ventilation airflow,
what is the maximum set point used, approximately, in parts per million, ppm.
1. 100
2. 700
3. 250
4. 1000
5. 5000