We have quite a few CO2 monitors in classrooms around the trust (and are a requirement in new builds). They are installed to give an early indication that levels are rising and this may lead to reduced levels of concentration in the pupils. Unless there are actual CO2 creating processes (such as open flames) it is extremely unlikely that levels will ever become dangerous as our classrooms are not so well sealed so as to allow a massive build up. The HSE exposure limits are below.

  • Long-term exposure limit (8-hr reference period) of 5000 ppm
  • Short-term exposure limit (15 minute reference period) of 15000 ppm
The lower end effects are
  • 250-350 ppm: background (normal) outdoor air level
  • 350-1,000 ppm: typical level found in occupied spaces with good air exchange
  • 1,000-2,000 ppm: level associated with complaints of drowsiness and poor air
  • 2,000-5,000 ppm: level associated with headaches, sleepiness, and stagnant, stale, stuffy air; poor concentration, loss of attention, increased heart rate and slight nausea may also be present.
  • >5,000 ppm: This indicates unusual air conditions where high levels of other gases also could be present. Toxicity or oxygen deprivation could occur. This is the permissible exposure limit for daily workplace exposures.
Generally they are set to alarm at 1500ppm. So an indication to let some fresh air in but nothing to panic about.

Hope that helps

Alastair

Alastair Sneddon

Estates Manager