EBME Forums Forums Maintenance Technical Assistance Entonox demand valves

What test procedure do other EBME's use for the testing of Entonox demand valves?

We use the BPR medical demand valves and they are described as maintenance free for 5 years at which point they require swapping out due to the hose degrading.

We do however do a basic leak on test them yearly, and then service exchange every 4 years.

I'm curious as to how often people check them and what test specs and tolerances are used.

Back in the days when BOC Entonox demand valves were ubiquitous, there was a quarterly minor service routine, followed by a major service once a year.

The major service (and, indeed, the one taught at Falfield) included stripping the unit and replacing certain parts (although the pipeline version was simpler - no pressure reducing valve). The famous A-frame Test Bellows was required

Who knows what is "permitted" these days! I guess you could check the plastic casing for cracks and (or) deterioration ... and also check the Bodok seal and contents gauge if you come across any connected to a cylinder.

It sounds like the plan you mention, plus a quick functional test, should suffice. Have you ever had one fail?

Thanks Geoff.

At this point we are trying to determine what "fail" actually means. What value of leak is permitted.

I have been told that the demand valves have to comply with BS4272-2 when produced. I can't find the details of the standard anywhere unfortunately (without paying for it!) - so if anybody can help there I would appreciate it.

I am led to believe there is a internal and an external leak tolerance. The internal being the demand valve itself and the external being the hose. I think the figures mentioned were something along the lines of 0.5mL/min

Connecting to a 4 bar supply with a mass flow meter in series seems the logical way to test for any leaks to me, i'm just wondering if anybody actually does this kind of test and over what time.

With the greener NHS programme in full swing we are looking at cutting down our nitrous and Entonox usage hence why we are looking at the demand valves.

We use Therapy Equipment demand valves and where needed the regulators. The demand valve has a service kit which is fitted every three years and we replace the hose at the same time. The Diamond regulator is easy to service every four years. The flow, pressure and leak tests are straight forward using readily available equipment.

The demand valves are fairly robust although they have changed the design to incorporate the handle and hose assembly.

For what it's worth, the old BOC test for pipeline Entonox demand valves did not worry too much about leaks ("... listen carefully at the patient outlet for leaks").

Instead, it recommended two "breathing resistance" tests - which, to my mind, are far more important from the patients' point of view.*

Both relied upon the afore-mentioned test bellows (BOC A-frame).


* I always liked to check-out kit (of all types) in a fashion that mimicked as closely as practicable actual "patient usage" (not too much fancy test kit about in those days).

Notice how low those negative "breaths" are:- 1.8, 14.7 and 22 mmHg respectively.

What flow, pressure and leak test spec/tolerances do you test to Adrian?

We used these in my previous role:
https://www.meditech.uk.com/product/entonox-demand-valve/

Very rugged design, could handle being dropped and had a 5 year service interval.