Indoor Air Quality (IAQ) in School Classrooms

The problem is foul air.

Breathing air that has been expelled from the lungs of thirty other occupants in a badly ventilated classroom is almost the very best way of spreading transmittable bacteria, between all occupants.

Given a choice, few parents would allow their children to drink dirty water, share cups, glasses, water bottles, or the food and cutlery of others.

In a classroom, unless the windows are widely open, or unless there is a forced air ventilation system, children are forced to breathe the foul and bacteria contaminated air from others.

Failure to provide a healthy indoor environment could have legal and negative publicity consequences.

The solution is ventilation.

Ventilation, in its truest form, means the collection and removal of contaminated air, and replacing that air with fresh outdoor air. Such ventilation dilutes contaminated air with fresh air and so reduces indoor air pollutants, and occupant exposure to foul air.

The most common buildings that have foul air are usually those with a small internal volume, a high occupancy rate, which results in excessive heat, and high humidity.  In such places, occupants are breathing air expelled from others lungs.

Most bacteria, and fungi, thrive in conditions that are moist and warm, cough colds and influenza spread by breathing contaminated air.  One person sneezes, atomised mucus and spittle contains the virus.  The atomised sneeze particles remain suspended in the air for an hour or more. Other occupants breathe the air containing the atomised particles and virus, and so the body fluids of one person can be directly inhaled by others.

The immune system of each individual has different levels of protection, but in a thirty person classroom there can be several types of bacteria, and it is inevitable that the bacteria will infect some or others, depending on the level of contagion.  Coughs colds and influenza are bad enough, and it says little for our general hygiene standards that these ills are accepted as a fact of life.

Most schools are aware of the dangers of meningitis, but little thought is given to the fact that meningitis can also be spread by too many occupants in a small, under ventilated space, sneezing, coughing, laughing, then breathing and sharing the same foul indoor air.

LEGAL REQUIREMENTS

It is against the law to knowingly expose the public to conditions that may endanger their health or well being. Just as exposure to physical danger on a construction site, or ”spiking" a drink is illegal and subject to penalties, so the same applies to exposure to contaminated air.

There have been cases where substantial damages have been awarded where foul air has affected health.

SCHOOL CLASSROOMS

To appreciate the conditions of the indoor environment of a school classroom, the difference between Indoor Air QUALITY and Indoor Air COMFORT needs to be understood (see the Quality versus Comfort link on the left)

See our links on the left for more web sites containing information on the problems of Indoor Air Quality (IAQ) in schools.

EXAMPLE SOLUTIONS

FIRST -- Identify the problem. --- Here are some complaints to choose from …….

A) In Summer the Classroom is too hot --- "stuffy" and it smells. There is no significant problem in winter. This classroom may be improved by a simple ventilation system, (Click Here for examples).

While the ventilation rate of 8 lps will provide indoor air quality, if the room has excessive summer heat, then to achieve summer indoor air comfort may require a ventilation rate at least three times 8 lps per occupant.
There is a vast difference between indoor air quality and indoor air comfort.

To achieve summer indoor air comfort by a simple ventilation system will automatically provide acceptable indoor air quality, but this system is unlikely to be usable in winter because valuable heat is wasted when the air is exhausted, and unless heated as it enters. The incoming fresh air will chill the classroom.

Installing air conditioning to cool the indoor environment, will ensure indoor air comfort, but unless the air conditioner also ventilates, at the rate of at least 8 lps per occupant, then acceptable indoor air quality will not be achieved.

For any solution the problem of noise has to be addressed.  Equipment in classrooms is required to operate at a measurable noise level of less than "NC35" this is a very difficult level to meet with environmental control equipment. (Many fluorescent lights make more noise than NC35).

B) In Summer the room is as described for A) above, and in winter the "stuffy" problem persists.

This room must be ventilated summer and winter. In summer, the ventilation rate must be above 8 lps per occupant to achieve indoor summer comfort and in winter, the ventilation rate must be not less than 8 lps, to maintain indoor air quality.

The only solution is a ventilation system that has the following features and benefits ……

• WINTER
1. Ventilation for indoor air quality to comply with NZS4303 (8 lps per occupant) or higher if the room has special ventilation needs i.e.….. Chemistry or science.
2. Energy Recovery, to prevent heat (in the exhaust air stream) being wasted in winter.
3. To maintain indoor comfort at not less than 16 °C (opening windows???)
4. To meet a noise level that is NC35 or less.
• SUMMER
1. Provide indoor air comfort (calculate the heat that has to be removed / controlled) and provide cooling or increased ventilation rates to achieve this.
2. If Air Conditioning is selected, ascertain that the system is designed to deliver IAQ -- 8 lps outdoor air, per occupant.
3. If Ventilation is selected, ensure that the rate of ventilation is at least 6 air changes of all the air in the room every hour (ACH). Depending on the amount of heat, it may be necessary to increase at a rate of up to 10 to 12 Air Changes per Hour. (ACH)
4. For either Air Conditioning or Ventilation, the equipment noise level has to be below NC35.

For this classroom, (with a summer and a winter problem) the best solution is an HRV (Heat Recovery Ventilator (also known as an Air to Air Heat Exchanger)).

Here is how it works …….

The HRV has three basic components ……

1. A Supply Air Fan (introduces 100% fresh air into the classroom at 8 lps / occupant)
2. An Exhaust fan (removes Stale Polluted air at the rate of 8lps / occupant)
3. An Air to Air Heat Exchanger which enables winter heat, that would other wise be exhausted, to be transferred from the exhaust air stream to the incoming fresh air stream, and so heats the incoming fresh air stream.

There are other "Add On" accessories that can enhance the performance of the HRV……

1. Higher performance fans - to increase the summer ventilation rate.
2. By-pass dampers - to improve Summer performance
3. Indirect evaporative cooling (EVCO) - Directly cools the incoming ventilation air without refrigeration (generally only applicable to East Coast NZ locations).