First - the term is SCBA notSCUBA. The SCUBA is for underwater use. When working for Cal/OSHA Iencountered a person trying to don the SCBA as an SCUBA. Fortunately, hewas inside a filtered operations room. This was in a huge gaseous phenol releaseso he didn't get hurt. He obviously was not trained in the properuse of the SCBA and the company was hit with a serious citation for it.
The SCBA is mandatory to enter an oxygendeficient room unless a handheld gas monitor is used to verify that actual oxygenconcentration is not hazardous. Pay attention to the local state OHSAregulations on oxygen deficient atmospheres so you don't get intotrouble. They are actually good common sense regulations to preventdeaths.
The oxygen room monitor needs to beinstalled according to regulations with the readout on the outside of the roomor building. The sensor must be recalibrated often due to thedeterioration of the sensor. It will need to be re-spanned at least each6 months to assure a good response to low levels of oxygen.
At the lab where I was the EHS officer, wehad a large liquid nitrogen leak in a room full of dewars containing biologicalspecimens. The alarm went off and we double checked the atmosphere byslightly opening the door and putting the handheld monitor inside. Thereadings were very low % and would have been deadly if entered. Especiallydangerous is a liquid nitrogen spill/leak due to its density which will pool onthe floor and easily rise to the nose level with asphyxiating consequences.
Training for the SCBA is regulated by OSHAand needs to be followed closely. If no person has accreditation fortraining on SCBAs, then a professional trainer will be necessary.
End result: Be very careful whendealing with asphyxiating gasses for they can and will bite you.
Ken Smith (former CIH, now retired)
From: DCHAS-L Discussion List[mailto:dchas-l**At_Symbol_Here**MED.CORNELL.EDU] On Behalf OfBarbara Wiehe
Sent: Wednesday, August 29, 201210:23 AM
Subject: Re: [DCHAS-L] OxygenSensor
Thankyou for your responses.
Neal, fair enough put the red flags away...I was thinking scuba but it isn'tgoing to fly with anyone here to go to that extent.
I appreciate getting feedback from your perspectives rather than push back fromothers.
On Wed, Aug 29, 2012 at 12:45 PM, Neal Langerman <neal**At_Symbol_Here**chemical-safety.com>wrote:
Severalthing - first and foremost The only protection for an oxygen deficientenvironment is a supplied air source. Thus, a question regarding"respirator fit" raises a flag.
Havingsupervised the installation of many oxygen sensors in locations where adeficiency can occur, here are some thoughts
Thesensor should be located IN the area to monitor and installed according to themanufacturer's instructions. Pay particular attention to thevertical height instruction.
Thesensor is low voltage, but the installation still must comply with the NEC.
Thealarm should be in the monitored area and repeated just outside the affectedzone and also at a central monitoring location.
Provideregular maintenance as required by the manufacturer. While using a twogas calibration to set the span works, some sensors are calibrated with ambientoxygen, set to 20.8%. It is very useful to periodically test the sensorwith a low oxygen source.
Mostelectrochemical oxygen sensors require replacement every two years. Inthe very dry climate of southern California, we find that they need morefrequent replacement.
Falsealarms from an oxygen sensor should be very infrequent. If false alarmsoccur with an annoying frequency, work with the manufacturer to fix it -false alarms lead to the "chicken little" problem.
Yourresponders to an alarm, be it maintenance or other, should bring a working4-gas portable with them to provide a back-up to the installed system.
Finally,installed sensors are really great, but they require active PM and someunderstanding of their limitations.
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ACSafety has a new address:
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We are installing an OxygenSensor in a room using Liquid Nitrogen. Question, why do you mount it inthe room where loss of Oxygen would be present? What type of trainingshould the technician have overseeing the monitor?(ie respirator fit)
Ohio Wesleyan University
Environmental Health and Safety / Greenhouse Manager
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