Gas monitoring cross sensitivities

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This topic contains 1 reply, has 2 voices, and was last updated by  Bob Stern 4 months, 4 weeks ago.

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    The Hazmat Guys
    The Hazmat Guys
    Joined 1 year ago
    online 3 days ago

    From one of the listeners. Lets give him a hand!

    We were originally dispatched to a CO alarm in a single-family residence and met the first in Engine at the address. The Captain informed us that they had readings of 150 ppm of CO showing on their Draeger CO monitor (4 gas monitor). It was approximately 80 degrees that evening (which is warm for us) so the furnace wasn’t running and there were no other gas appliances in the house other than the hot water tank. We entered the structure and our CO detector immediately climbed to 150 ppm, as well, our Phosphene detector (4 gas monitor) went into low alarm. The homeowner advised us they had just had an air conditioner installed two days before, and this was the first day that they actually were running it. We then brought in our refrigerant detector, and immediately got readings of 80 ppm of the refrigerant 410A. The gas utility service worker confirmed that the hot water tank was not the cause of the high CO levels and we concluded that the air conditioner was the cause of the alarms. Not knowing anything about air conditioning units, we ventilated the structure and advised the homeowner to sleep somewhere else until a qualified HVAC technician could service the AC unit. Here are my questions.

    Have you encountered refrigerants giving a false positive on CO detectors ?
    Have you encountered refrigerants giving a false positive for Phosphene?


    Bob Stern
    Joined 4 months ago
    online 4 months ago

    This is definitely a scenario for picking either the right sensor or maybe take in more than one. I have many examples of this type of call where an IMS based detector (to be named if you ask) was used to locate the source of the vapor. That is really what you need to do when you get multiple differing alarms that do not fit each other. In this case, if the installation of the air conditioner had a bad fitting and refrigerant was the cause of the situation, the instant reading, IMS unit, would find the leak.

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