The effects of CO2 on adults at good health can be summarised to:
⦁ normal outdoor level: 350 – 450 ppm
⦁ acceptable levels: < 600 ppm
⦁ complaints of stiffness and odours: 600 – 1000 ppm
⦁ ASHRAE and OSHA standards: 1000 ppm
⦁ general drowsiness: 1000 – 2500 ppm
⦁ adverse health effects may be expected: 2500 – 5000 ppm
⦁ maximum allowed concentration within a 8 hour working period: 5000 – 10000 ppm
⦁ maximum allowed concentration within a 15 minute working period: 30000 ppm

Maintaining healthy CO2 levels by ensuring correct ventilation levels, whilst maintaining temperature, is important for the welfare and productivity of staff.