LAS VEGAS - Carbon monoxide (CO) poisoning is a danger that homeowners and business owners face every day in their indoor environments. It is also a subject that HVACR contractors need to know as much about as possible - for their own safety, as well as the safety of their customers and employees. That is the message that Frank Besednjak brought to ISH NA seminar attendees.

Besednjak, a consultant for The Training Source Inc., Mt. Washington, Ky., titled his presentation "Carbon Monoxide - Your Role as a Contractor."

"The Center for Disease Control said there are over 40,000 hospital emergency department visits for CO poisoning each year," he said. "One thousand people die each year from CO poisoning."

Besednjak said that many more people are hospitalized because of slow, gradual exposure to CO. "Low levels of CO exposure cause neurological problems, rather than one catastrophic incident that sends someone to the hospital emergency room right away.

"For every case of CO poisoning that is reported, there are 10 cases that go unreported."

What Contractors Can Do

"Technicians should always check for CO as part of their normal routine," stated Besednjak. "Individual exhaust ports on the furnace need to be tested."

He said that technicians should be allowed to drill a hole in the flue vent to test the air but that some localities do not allow this form of testing. "If you are not allowed to drill the flue vent hole, the local authority needs to sign off on it," he said.

Besednjak stressed that it is important for technicians to know where to test for CO. Since it is a colorless and odorless gas, locating it within a confined space is not automatic.

"The first place that CO goes is toward the ceiling because it has been warmed by a combustion appliance," he said. "Eventually it will cool off and lower itself to the floor as it mixes with the air. Make sure you measure toward the ceiling and the floor.

"And CO detectors [in the customer's home] should go toward the ceiling. But advise customers to read what the manufacturer recommends."

He also said, "Remember that the smaller the home, the higher the potential for high levels of CO, which is put out by combustion appliances."

Besednjak added some tips on measuring CO. "Measurements should be made when the appliance is in a steady state of generation," he said. "The appliance should have cycled off and cycled back on again.

"Zero out your instruments on the outside of the building because you need to know the difference between the indoor environment and the outdoor environment."

Besednjak also said it is important to communicate with homeowners and building owners about CO measurements. "Always talk with your customers about your findings and make recommendations if possible," he suggested.

For more information on The Training Source Inc., including downloadable CO PowerPoint presentations, visit or e-mail Besednjak at

Publication date: 12/08/2003