In a classroom where CO₂ levels are high, students will probably be less attentive and concentrate less well. There is, however, an answer, says Tim Kaye
Our best efforts and intentions are sometimes influenced by that powerful, unwritten rule; the law of unintended consequences. It's designed to catch us out when we are trying to do the right thing.

Ironically, this is what has happened with the laws and regulations aimed at reducing carbon dioxide (CO₂) levels to tackle global warming, which has had the side effect of raising CO₂ levels within buildings, leading to a significant lowering of mental performance.

Drop-off in performance

This may not sound a major problem, but it can lead to carelessness and accidents in the home and workplace, and, a number of studies have shown, significant drop-offs in performance in schools and offices.

The unintended cause of the problem has been the drive to insulate buildings and eliminate draughts. As we all know, the benefits of this are enormous in terms of cost and energy saving, as expensively produced heat is more efficiently held within the building.

Warm air is not constantly leaking out while cold air seeps in, and reduction in energy consumption leads to a consequent fall in the amount of CO₂ produced by burning fossil fuels.

The problem is that the CO₂ produced during normal respiration is also trapped in the building, along with the heat. If windows are opened or normal ventilation installed, the heat flows out along with the CO₂.

Heat recovery ventilation

This is why I believe the only real option is heat recovery ventilation, a message we are initially trying to get across to schools and modern modular offices, as this is where we think there is the biggest problem and where we believe the most benefits can be reaped.

The size of the problem being caused by high CO₂ levels is clearly shown by the results of a number of studies carried out in schools.

A 2004 study by the University of Exeter entitled 'The Effect Of Low Ventilation Rates On The Cognitive Function Of A Primary School Class' found that: 'The attentional processes of school children are significantly slower when the level of CO₂ in classrooms is high.'

The study measured the results of children performing a number of simple tests and used the 'Power of Attention Factor' which represented the intensity of concentration at a particular moment. Faster responses reflected higher levels of focused attention. Increased levels of CO₂ led to a decrease in this factor of around 5 per cent.

'Thus,' says the conclusion of the study, 'in a classroom where CO₂ levels are high, students are likely to be less attentive and concentrate less well on what the teacher is saying, which, over time may possibly lead to detrimental effects on learning and educational attainment. The size of this decrement is of a similar magnitude to that observed over the course of a morning when students skip breakfast.'

For the UK, the recommendations on the amount of fresh air required in schools are enshrined in Building Bulletin 101, which requires a background fresh air supply rate of 3l/s per pupil with the capacity to boost this up to 8l/s per pupil. It also states that the concentration of CO₂ in classrooms should not exceed an average of 1,500ppm over the school day. A number of studies have suggested that these levels are not being met.

Kim Jensen, a founder of Airmaster explains: 'The fresh air required in schools in Denmark is based on the concentration level of CO₂ rather than the amount of air required per person. This ensures excellent indoor air quality remains constant throughout the day.'

In one school in Denmark, CO₂ levels were logged at over 4,000ppm. After installing heat recovery ventilation, this level was reduced to less than 1,100ppm.

A Scandinavian study in 2010, entitled 'Problems with Classroom Air Quality' clearly showed that doubling the outdoor air supply rate improved performance in a sample of pupils by 8-14 per cent.

There is, of course, the question of why, in these times of cut-backs, hard pressed schools should spend public money on heat recovery equipment. Personally, I believe the improvement in the performance of our children makes the comparatively small expense well worth while. However, for those who need further incentive, I would point out that large cost savings can also be achieved.

Significant savings

While these studies were carried out in schools, the results apply just as much in other applications such as homes, offices and other work places.

With efficient equipment, up to 84 per cent of the heat in air being extracted is recovered and used to warm the fresh air supplied into the room.

For example, if the outside air is -2 deg C and the inside has been heated to 22 deg C, then the recovered heat would warm the air supplied to 18 deg C, providing a significant saving in heating costs.

One answer to CO₂ build-up
Airmaster X-Vent is a range of heat recovery ventilation units needing no ductwork or diffusers. The products can supply between 180 and 1,200 cu m/h of fresh, filtered outdoor air.

Multiple X-Vent units can be controlled individually or centrally using either a programmable weekly timer or integrated CO₂ sensors. The sensors continuously monitor the CO₂ levels in the room and increase or decrease the supply air as required.

The Airmaster X-Vent comes in a range of sizes and mounting options. With surface mounted or partially integrated models available, the plug and play unit is claimed to be easy to install, simple to operate and efficient to run.

• Tim Kaye is sales director of Airmaster Applied Solutions