Carbon monoxide found in tanks

[aviator8]

I've plumbed in a Sensorcon CO detector on my compressor for real-time monitoring.... It is a very comforting feeling seeing "Zero" when filling.... I have been curious to plumb in a sample point before my filtration to see what the compressor is doing, but haven't made the investment yet.

I also have a CooTwo for when I use "other people's tanks" (though i need to send it back for some software update as it is the original from the funding campaign)...

what is the lifespan of the sensorcon? I cant seem to find it anywhere.

 

[DandyDon]

what is the lifespan of the sensorcon? I cant seem to find it anywhere.

I send mine back for battery & sensor replacement every 24 months, then tag it with a dated sticker. The accuracy will drift somewhat, but I use is as an alert. The CooTwo is more accurate.

 

[rjack321]

Personally I would not dive more than 2 ppm. I am not calling you crazy - I just believe CO should not be in the tank.
Partial Pressure is what will kill you - and you are taking a big chance unless you are diving 5 feet deep. Go with 0 CO and accept 2 ppm if you must...


You have this backwards - 10 PPM for all residential CO detectors in the US. Production / factory lines will allow 50 ppm for an 8 to 12 hour shift. Still not healthy but factories are hard to bring 50 ppm down to residential standards...

I do this all day long every day - someone is either forgetting to change a battery or the CO detector is out of date.
I would never let an infant or older person stay in the home with more than 10 ppm - find the issue or call the gas company and let them find it and fix it.

YMMV...

First of all I didn't say I would dive 18ppm. I said it was unlikely to kill you on a recreational dive. I accept up to 2ppm on my meter which is about what I can bump test it to with my breathe (2-3ppm is normal for a nonsmoker to exhale). I can't think of a tank I have tested >1ppm however which I attributed to really high ambient temps and random sensor drift.

Second there is no "standard" for home CO detectors other than the UL test which is weak. And even if there was one its not 10ppm.
@2airishuman is correct.

The UL standards for home CO monitors are here:
Carbon Monoxide Levels & Standards for Detectors

Copied here for you:
So when will a UL/CSA-listed carbon monoxide detector alert us to dangerous levels of CO being present? Here’s the summary:

• 0 – 29 ppm The detector must remain silent. If it has a digital display, it
  must show a zero reading. It may show the actual reading, but
  only if the user presses a button.
• 30 – 69 ppm If the carbon monoxide level remains in this range for 30 days, the audible alarm may sound. If a digital display is present, it should show the actual CO level as long as it is 30 ppm or higher.
• 70 – 149 ppm If the carbon monoxide level remains in this range for 1 to 4 hours, the alarm must sound.
• 150 – 399 ppm The alarm must sound if the carbon monoxide level remains in this range for 10 to 50 minutes.
• 400 ppm + The alarm must sound if and only if the carbon monoxide level remains at this level for four minutes and no more than 15 minutes.

Bottom Line: Your UL/CSA-listed carbon monoxide detector will not sound an alarm until you have been exposed to far more carbon monoxide than all of the exposure limits established by the various organizations listed previously.


Home CO meters all operate on a time weighted average principle. Most don't alarm as all at 10ppm since this level is fairly common in indoor air, especially homes using natural gas & propane applicances with no venting like a stove. Alarms typically begin around 50ppm but for longer exposures (hour+). A short term 200ppm alarm - ie any instantaneous reading >200ppm is common but sometimes those short term alarms are set higher. Like 1min >200ppm or any instantaneous reading >400ppm. The 200ppm is derived from the NIOSH and OSHA maximum permissible instantaneous level.
CDC - Immediately Dangerous to Life or Health Concentrations (IDLH): Carbon monoxide - NIOSH Publications and Products
The 50ppm is an 8hr time weighted average level for the entire workday from OSHA.

Getting workplace exposures down to 10ppm (on average?, max?) is admirable but not required.

 

[rhwestfall]

I send mine back for battery & sensor replacement every 24 months, then tag it with a dated sticker. The accuracy will drift somewhat, but I use is as an alert. The CooTwo is more accurate.

Sensorcon: I calibrate mine with a calibration bump gas monthly. Mine is a brand new unit...

YMMV

 

[Basking Ridge Diver]

Second there is no "standard" for home CO detectors other than the UL test which is weak. And even if there was one its not 10ppm.
@2airishuma

Ok so I am going to apologize - we have an SOG that states 9 ppm or below is all we are allowed to allow residence in the home - otherwise we evacuate and figure out the source. My misunderstanding - I "assumed" 9 ppm is what set off the alarm - it is not.
Thank you for clarifying for myself and others that may read this thread. I was wrong.

 

[2airishuman]

Well, to be fair, there has been a recent "dumbing down" of residential carbon monoxide detectors. Earlier ones were, on the whole, more sensitive, and there was a plague of people calling the fire department out from co levels caused by someone starting a car in the garage and (promptly) driving away.

As a society we decided to solve this problem by making residential CO detectors less sensitive.

Evidence does exist that CO is hazardous even at lower levels, particularly with chronic exposure. There was an effort by OSHA to reduce the PEL from 50 ppm to 35 ppm, in 1988, which was overturned by the courts.

 

[rjack321]

Ok so I am going to apologize - we have an SOG that states 9 ppm or below is all we are allowed to allow residence in the home - otherwise we evacuate and figure out the source. My misunderstanding - I "assumed" 9 ppm is what set off the alarm - it is not.
Thank you for clarifying for myself and others that may read this thread. I was wrong.

Oh I agree having >10ppm persistently (days/months) in a house isn't a good idea. Most meters are dumbed down to avoid this being a "false alarm" though. I wouldn't want the elderly or asthmatics or heart diseased etc to be exposed to 25ppm 24/7 that's for sure. The 35 ppm is only for 8hrs a day at work for a healthy person with 16hrs of "fresh" air at home (which NIOSH and OSHA fail to appreciate might have as poor air quality as the workplace so the 35ppm might actually be 20hrs/day).

18ppm for an hour at 3 ATA would probably make you nauseous and headachy but I doubt would be fatal. But scuba air should be better than just not fatal since its really easy to make 0ppm CO gas.

 

[W W Meixner]

I went diving this past weekend and, as I have been doing for a while know, I took my CO analyser with me. I was diving with an OP I trust and did not expect to find any trace of carbon monoxide. Still, I went on and tested the tanks.


First, it was my buddy's tanks (doubles) that were analysed. No carbon monoxide found. Then I went for mine. The device started to beep and indicated 18 ppm. I repeated the tests on both sets of doubles, with the same results. I talked to the OP manager and tested two other sets. The first red 7 ppm and the other, 0. The manager apologised and asked for my analyser to check other tanks. Some time later, he came back to me and said he believes the contaminated tanks were a group of five that had been on lent for another OP. Still, he promised to go over the OPs procedures regarding CO control.

What really surprised me that day was my experience with another diver setting up beside me, who I believe to be and instructor. When I detected CO in my tanks, I told him that and offered my analyser for him to check his gas. He told me he couldn't smell anything strange in his tanks and said he did not want to use the analyser.


edit: spelling

N...

As has already been mentioned...I would suspect a faulty compressor from wherever your cylinders were filled last...

If there is an odor in the cylinders...it is not CO..but hydrocarbon residue...likely compressor oil...

If your diving enriched oxygen mixes...would stongly suggest having your cylinders re-O2 cleaned...only way to be sure...

If they were my cylinders...I'd O2 clean them whether I was diving with EAN or not...there should be no odor...

Best...

Warren

 

[Nirvana]

N...

As has already been mentioned...I would suspect a faulty compressor from wherever your cylinders were filled last...

If there is an odor in the cylinders...it is not CO..but hydrocarbon residue...likely compressor oil...

If your diving enriched oxygen mixes...would stongly suggest having your cylinders re-O2 cleaned...only way to be sure...

If they were my cylinders...I'd O2 clean them whether I was diving with EAN or not...there should be no odor...

Best...

Warren

They were not my cylinders; I was renting them for the dives. I used another set, that tested free of CO. The contaminated tanks were taken by the operator to be further inspected.

As for CO not being detectable by smell, I know that. That is one of the reasons why I brought an analyser with me . In fact, as I tried to convey before, I was taken aback by the reaction of the instructor beside me, who seemed to have an absolute confidence that he’d be able to smell any dangerous contaminant, apparently including carbon monoxide.

 

[Basking Ridge Diver]

One last point - I found out where our 9 ppm for residential occupancy was coming from in the SOG. Ashrae is The American Society of Heating, Refrigerating and Air-Conditioning Engineers is an American professional association seeking to advance heating, ventilation, air conditioning and refrigeration systems design and construction. ASHRAE has more than 57,000 members in more than 132 countries worldwide.

https://www.ashrae.org/File Library/Technical Resources/Technical FAQs/TC-04.03-FAQ-34.pdf