Some HVAC contractors have responded by offering CO safety inspections and even becoming certified to do so. Others send their technicians to classes on equipment inspection methods, like the recent heat exchanger inspection seminar held by the Western Pennsylvania Chapter of the Air Conditioning Contractors of America (ACCA-WPA). It was presented by Ellis Prach of Heat Exchanger Experts, Fort Collins, Colo.

Several contractors interviewed by The News said they now measure CO levels on all heating system calls for the sake of liability protection. Still others perform CO inspections because of local codes. All said they want to help protect the health and safety of their customers.

Technician Training

The certification addresses all aspects of carbon monoxide inspections: equipment requirements, proposed action levels, and inspection protocols. Nebrasky and his staff completed a two-hour written exam and 30-minute hands-on demonstration of CO knowledge, detection, and solutions required to become certified Carbon Monoxide Analysts.

Nebrasky said he started checking for CO more regularly in 1995.

“When I was in the field, I would go into people’s houses and these people had headaches, or I got headaches working there,” he said.

Now, “We test on every one of our service calls,” he said. Although people “sometimes get very nervous” when they hear the results, if a customer has called for a CO inspection, they may already suspect there is a problem. Moreover, if it’s an emergency case and the customer has already called the gas company or fire department, they usually have already opened all the doors and windows per emergency instructions.

“Usually when we get to their house, it is already very well vented,” he said.

When techs find high levels of CO, “We tell [customers] the truth.” A high-tech measuring device also provides a printout of the CO measurements. “We tell them how we’re going to fix it.”

William Bimeal of Max C. Smith Co., Gibsonia, Pa., sent one technician to the recent ACCA-WPA seminar. Several of his employees have also taken part in training through Bacharach, a manufacturer of portable instruments for combustion safety source leak detection.

CO detection is “very important from a liability standpoint,” said Bimeal. “A lot of my competition does CO detection, but that is not the reason we do it. It is for the well-being of consumers.”

Bimeal said his technicians are trained to perform CO readings on every furnace check and before any other work is done. He also said that each year, more of his customers request a check of CO levels in their home when they call for a regular furnace check.

This is one of the reasons why Ellis Prach has made it his business to educate contractors and techs about checking heat exchangers. Prach said that although heat exchanger cracks do not cause CO to occur, they could contribute to a larger problem.

Measure, Then Look

“Everyone has learned from someone who doesn’t know how to do it,” is how he put it.

Checking a heat exchanger is simple, he continued, if you know what to look for.

“You need to know where to look in the heat exchanger. They all fail in the same place,” he said.

For example, Prach said clam-shell-style chambers tend to crack in the back. With serpentine chambers, a good clue that cracking has occurred is if the eyelets have popped off.

There are several reasons why a heat exchanger would crack, including lack of combustion air and improper temperature rises, Prach said. He said that checking the heat exchanger is an important part of every CO inspection, even for newer heating systems.

Bob Dwyer, instructor and developer of Bacharach’s CO, combustion analyses, and building pressure training, said that a crack in a heat exchanger is a small part of a complete CO inspection.

“Just because there is a crack in the heat exchanger doesn’t mean that there will be a CO problem,” he explained. “If the furnace has cracks and is not producing CO, you can determine whether or not you need to shut down that system.”

If there is no evidence that the furnace is producing CO, you may not need to shut it down — but to be on the safe side, Dwyer recommended placing CO alarms near the furnace.

The basic thing to remember, he continued, is that carbon monoxide is produced from unburned fuel (incomplete combustion). A specific amount of oxygen and degree of temperature must be present for combustion to occur. If the system was not installed to factory specifications and combustion is incomplete, all of the fuel will not be burned off. This creates CO.

Dwyer said a variety of tests should be performed on every furnace inspection. First, “You have to go into the area with your CO detector running,” he said. “If the reading jumps up, you can already suspect there is a problem.” The technician must then find out where the excess CO is coming from, and whether the furnace is at fault.

In gas- or oil-burning systems, Dwyer said technicians must check fuel pressure. They must also check manufacturer specifications. For example, technicians must make sure that orifices or nozzles have been sized correctly.

With a combustion analyzer, technicians must check that air and fuel mixtures are measurable to guarantee that combustion air is adequate. All combustion equipment flue gases are measured for CO before dilution air inlets. Dwyer said that if a combustion system does not have a draft hood, a hole must be drilled in the vent connector of the system and gases may be measured. The access hole must then be sealed to vent manufacturer specifications. Next, technicians must make sure that systems with vents draft without interruption and are installed to the manufacturer’s sizing requirements.

Dwyer said there is a misconception that drilling holes in vent connectors is not approved by manufacturers. He said that some B-vent manufacturers have acknowledged that it is important to take flue gas measurements, and that the type of vent used should not prevent tests from being taken.

Nebrasky pointed out that in cases where there isn’t enough combustion air, the furnace is installed in a finished basement, where the furnace is relegated to a small room with a limited amount of air available.

Bud Chick, owner of Sheridan Mechanical Services, Englewood, Colo., added that when dryers are added in the proximity of the furnace or boiler, this reduces the amount of combustion air still more.

In general, heating technicians need to look for venting and examine flame color, the chimney, CO connections, and the condition of the heat exchanger. They should also check the gas pressure to the unit, which could be problematic due to utility service or improperly operating gas valves, Nebrasky pointed out.

Bimeal said there are several locations in the home where CO can be produced. If CO is detected, and the source is not from the furnace or the water heater, Bimeal’s technicians will check other potential areas, such as fireplaces. If a return register is near the fireplace, CO can be introduced into the ventilation system and delivered to other areas of the home. Attached garages can also be CO sources.

Bob Boyle, president of Phillips Heating and Air Conditioning, Pittsburgh, pointed out that if a vent pipe becomes disconnected or something falls into the chimney, CO can back up into the home.

Boyle said that the first thing to do is to clean the system and make sure that the furnace undergoes regular maintenance. This can help reduce the amount of CO that is produced. If CO levels are still high, Boyle said the consumer should look into getting a new furnace. At the very least, CO alarms should be added throughout the house until the old furnace can be replaced.

Old Furnace, New Homeowner

“The flue went into the crawlspace and to the chimney,” Nebrasky said. When he went into the crawlspace, he saw that the flue was disconnected “and was spewing out carbon monoxide.”

Cases like this are, in part, the reason behind the creation of safety codes. In the Denver area, for instance, before someone can sell their house, they have to have their furnace certified, according to Chick.

“In addition to a thorough CO check, the power company can perform an inert gas test to check the furnace cabinet’s integrity. They fill each heat exchanger with a mix of nitrogen and propane,” said Chick, and these are measured at duct grilles throughout the house.

“There’s not a furnace that’s so tight that no gas escapes. Some furnaces that are flunked based on that inert gas test, passed the CO test.”

He said he evaluates furnaces based on the CO inspection, commenting on the cleanness of burners, combustion air, heat exchanger, etc.

Chick said that although this furnace inspection requirement probably was started with good intentions, with the inert gas test, it is now used as a device for the buyer to drive down the cost of the house or get a new furnace. Even if a heating unit passes a CO test, the buyer can call the local utility to perform the inert gas test; chances are good, said Chick, that the furnace will fail that test.

Regardless of a city’s or county’s codes, “We measure CO automatically,” said Chick, “even on new installations.” In addition to the liability protection documented CO testing offers, it confirms that the new unit is receiving ample combustion air.

Boyle said a recent furnace inspection indicated small cracks in the heat exchanger. The cracks were leaking two parts per million (ppm) of CO. This is a minimal amount, but Boyle said the customer had to be warned and presented with options.

“The customer had just bought the house and wanted to know if they could wait a year,” said Boyle. “But you don’t know at what point it will get worse.”

The company recommended that the consumer either replace the heat exchanger or install a new furnace. “You don’t want to be there telling them the sky is falling, but if there is a safety issue, you need to address it.”

Publication date: 09/22/2003