CFM Carbon Monoxide Sensors

JimGPE_13

(Sorry - topic should say CEM not CFM)

Does anyone have any experience with this particular product with respect to accuracy, reliability, stability, etc? They are almost always for sale on Ebay for under $150 which is my price range for this.

Any experience?

Thanks.

Jim Davis_3

CEM

Don't waste your money!!

JimGPE_13

Wow!

Okay, can you expand on that a bit? Is it the wrong technology? If so, what should I be looking for?

Do I really have to spend hundreds to find out if the carbon monoxide in a room is zero or 15 ppm? I don't need to differentiate between 3 and 4 ppm, I just want to know if a furnace heat exchanger is leaking, that sort of thing.

Thanks.

Jim Davis_3

CO Monitors

Besides not being as accurate as more expensive meters, most handheld space sensing monitors are temperature sensitive. A rapid change in the air temperature across the sensor can cause it to read CO even when none exists. Also I have found that checking for cracked heat exchangers in the duct work or at registers is rarely a valid test. CO rapidly dilutes as it enters free air outside the heat exchanger. I have seen furnaces producing over 3000ppm before the drafthood but as it mixes with room air going up the flue the reading have been diluted 100 to 1, or 30ppm. In the duct this dilution could even be greater. Now one has to verify the equipment is making high levels before the test has any chance or we can mess with the burner to make it produce high levels. This can be life threatening to the tester and the occupants of the building which is not a method of testing I would ever recommend. It is much better to measure in the outlet of the heat exchanger, before dilution air and determine if the appliance is operating safe in the first place. There are methods to detect for cracks this way but again there are several steps and procedures that must be taken to validate this test. Even this test could miss 50% of all cracks. The fact that water heaters probably poison more people than furnaces, makes checking for only cracked heat exchangers a minimal safety check.

Brian_24

Jim Davis ROCKS

JimGPE_14

One more pass...

You understand I am hoping to use this device to check for CO in the occupied space, not to set up the furnace or water heater combustion. I'm looking for occupant safety, not proper burner operation. In that case, such a detector would pick up CO from whatever source, the water heater, the furnace or an automobile idling in the garage.

What say you now?

Thanks.

Jim.

Jim Davis_3

Personal Sfety Meter

As long as you are using this as a personal safety meter and do not imply that this in any way indicates the safety of the equipment in the building, then it would be sufficient. Do not use it near any heat source.

JimGPE_14

Yes

Just looking for CO in the living space. What goes up the chimney is for the service guys. Similar to what the fire department does when someone's CO detector goes off and they show up to see if there really is CO in the space or if it was a false alarm.

Occupied space testing only.

Jim Davis_3

Space testing

If the space is ventilated prior to arrival this test can be misleading. If the test is conducted several hours after an incident and equipment has been turned off and the space hasn't been ventilated, natural ventilation may remove the detectable problem. Measureable CO in the space can take hours after equipment has been turned back on and the space has been ventilated. Space testing only indicates the present environment, not the previous or the next.