As I read posts and comments within social media HVAC groups regarding indoor air quality or IAQ it is clear that most technicians are focused on clean, healthy homes for their customers and their own families.  The main discussion revolves around filtration systems, temperature, humidity and air purification.  There is a forgotten element within IAQ that should not be overlooked and plays a very important role in how people feel, that forgotten element is carbon dioxide or CO2.  High levels of CO2 can cause headaches and fatigue, amongst other things.  The chart below gives us some info regarding safe and dangerous levels.  

Normal CO2 Levels

The effects of CO2 on adults at good health can be summarized to:

  • normal outdoor level: 350 – 450 ppm
  • acceptable levels: < 600 ppm
  • complaints of stiffness and odors: 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

Info from https://www.engineeringtoolbox.com/co2-comfort-level-d_1024.html

The video below explains how we can test for CO2 within a customer’s home or building using the Testo 440 and 323 Air Quality Probe.  

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Gary McCreadie

Gary McCreadie is an HVAC tech, the creator of hvacknowitall.com, the HVAC Know It All Podcast, and owner of McCreadie HVAC & Refrigeration Services

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HVAC Know It All was created by Gary McCreadie, a licensed refrigeration and gas technician, with three goals in mind:
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