I've tried the usual searches and had no luck so I hope someone on the forum will be able to help!

We have low oxygen alarms in areas containing for example liquid nitrogen and we carry out routine tests to check the sensor is responding correctly. At the moment this involves someone breathing on the sensor until the oxygen level drops far enough to set off the alarm.

This is not ideal so I was hoping someone is aware of a product we can buy to carry out these tests. Some sort of gas canister with low levels of oxygen seems obvious but it needs to be something that's not harmful in itself and preferably something easily portable.

Can anyone suggest something suitable?

Thanks!

Thank you Jane.

The length of time required to breathe onto the sensor is an issue and has lead to dizziness etc. so not ideal...

The people carrying out the tests are not the same people working with liquid nitrogen so I'd rather avoid the need for them to dispense it into a small container for the tests although this is one option we have considered.

Marcus,
In a previous life I have done much of this type of work. First of all most chemical oxygen sensors have a limited shelf life even if the equipment is switched off, the sensor relies on a chemical reaction. The sensor deteriorate,s over the life of the sensor and requires regular calibration to ensure the accuracy of the equipment. Most of the major equipment manufacturers supply a full range of parts, service agrements and of course the test kits that you are referring to. May I also suggest that you talk to the equipment supplier and arrange a service, maintenance contract. The manufacturers will usually provide free training on the adjustment of their equipment. make sure that this is documented with attendance certificates for obvious reasons. One suggestion may also be that you consider disposable personnel alarms. They are extremely low cost these days and are simply thrown away when they reach the end of their viable sensor life.

I dont know anything of your background, so please excuse me if it sounds like I am over egging the pudding (Not a pun from the food industry) but the consequences of getting this wrong are serious.

The other thing that has not been mentioned is the reason for the potential drop in oxygen levels and therefore a full risk assessment will obviously have been completed to identify these other hazards

I have not suggested a particularly supplier because you do not mention who manufactured your instruments!

I take your point Marcus - my experience is that on the hand-held monitors one breath is usually enough to set them off.

I could be wrong, but I thought that divers used a mixture rich in helium. Most oxygen sensors behave in a non-linear fashion in helium.

I like Mick's idea - cheap, effective and no-where near as heavy as even a small gas cylinder.

Thomas is also right to point out that you should have a risk assessment. That should have addressed the possibilities of avoiding an asphyxiating atmosphere in the first place.

As a last thought - what often happens is that people either become blase about the monitor and ignore it when it does go off or, worse still, turn it off because they don't like the noise.

It's actually fixed monitoring systems I'm talking about - they require quite a bit more puff to activate!

We do have risk assessments for this! We are following all the systems in place to minimise the risk, the monitors and alarms are an extra step. The alarms are loud enough in the locations I'm discussing that no one will be ignoring them and they can't be reset manually without a key that is stored securely.

The 'confidence' gases Phil has mentioned sounds like the sort of thing we need.

Thank you to everyone for your suggestions - given me some new ideas if nothing else.