Extech CO250 Portable Indoor Air Quality CO2 Meter

• Checks for Carbon Dioxide (CO₂) concentrations
• Calculates statistical weighted averages of TWA (8 hour time weighted average) and STEL (15 minute short term exposure limit)
• Maintenance free NDIR (non-dispersive infrared) CO₂ sensor

CO₂ Guidelines:

Non-Enforced Reference levels:

• 250 – 350 ppm – background (normal) outdoor air level
• 350- 1,000 ppm – typical level found in occupied spaces with good air
• 1,000 – 2,000 ppm – level associated with complaints of drowsiness and poor
• 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
• >5,000 ppm – Exposure may lead to serious oxygen deprivation resulting in permanent brain damage, coma and even

Regulatory exposure limits:

ASHRAE Standard 62-1989: 1000ppm: CO₂ concentration in occupied building should not exceed 1000ppm.

OSHA: 5000ppm: Time weighted average over five 8-hour work days should not exceed 5000ppm

Building bulletin 101 (Bb101): 1500ppm. UK standards for schools say that CO₂ at averaged over the whole day(i.e. 9am to 3.30 pm) should not exceed 1500ppm.

Germany, Japan, Australia, UK…: 5000ppm, 8 hours weighted average in occupational exposure limit is 5000ppm.