Air Quality

Air quality

1. NZ Standard 4303:1990 specifies minimum ventilation rates and indoor air quality.

2. Temperature and humidity are often said to have the most effect on indoor air quality because their levels can promote or inhibit the presence of bacteria or mold. Absenteeism was reduced in schools by 20% in Canada as the relative humidity in the facilities was increased from 22% to 35%. Student performance at mental tasks is affected by changes in temperature.

3. Schools need especially good ventilation as children breathe a greater volume of air in proportion to their body weight and because schools have much less floor space per person than found in most office buildings.

4. One of the first symptoms of poor ventilation is a build up of carbon dioxide caused by human respiration.

Mark Schneider November 2002.

5. The US Environmental Protection Agency has issued and IAQ tool kit for schools.

The following information is extracted from his kit.

• Indoor air quality is something that can be subtle and not always noticed.
• It is not always expensive to fix.
• It can be caused by moisture, dirt and warmth creating fungal problems such as mold and mildew.
• Students with asthma are sensitive to IAQ
• Temperature and relative humidity effect comfort and IAQ. Opening windows and changing thermostat settings to control temporary fluctuations in temperature can worsen comfort problems.

6. Air quality has not in the past been a significant issue in NZ although a lot of attention has been paid to this overseas. Research was carried out by the Building Research Association of NZ (BRANZ) of the winter ventilation of 24 classrooms in 12 primary schools in 1998. This research indicted:

• Air contaminants measured in twelve classrooms indicated concentrations fungi and bacteria associated with damp conditions. This suggests that indoor moisture control may be as much an issue in classrooms as with other naturally ventilated buildings in NZ.
• Average carbon dioxide levels were higher than the design targets for mechanically ventilated buildings. Although this is not directly a health issue, the measured carbon dioxide levels indicate that ventilation rates may not deal effectively with bio-effluents.
• Modern stand-alone classrooms are more airtight than older examples, following a similar trend in New Zealand residential buildings, were improved air tightness is associated with sheet interior lining materials and tight fitting window and door joinery.
• Ventilation rates estimated from metabolic carbon dioxide are appreciably higher than infiltration rates estimated from air tightness measurements, but are generally below the ventilation rate targets set for mechanically ventilated buildings.