Measuring gas in confined spaces – perhaps the most common question we get to answer at BaSystemen. In this article BaSystemen covers, briefly and to the point:
- What do the regulations say about confined spaces?
- Which options are there to detect gas at an early stage?
Figures
Between 1998 and 2014, 79 accidents in confined spaces were reported to the Dutch Labour Inspectorate (ISZW). Only 3% of all victims left the space without any form of injury, while 23% died.
In 56% of confined space accidents, hazardous substances in the atmosphere were not detected in time.
And that is why this blog is on our website.
What do the regulations say about confined spaces?
The Dutch Working Conditions Decree states the following:
- ‘’If it can be presumed that the atmosphere in a space contains substances to such an extent that this creates a risk of asphyxiation, narcosis, poisoning, fire or explosion, the employee may only be present in that space if an examination shows that the hazard is not present.’’.
- If the examination referred to in the first paragraph shows that a risk of asphyxiation, narcosis, poisoning, fire or explosion is present, effective measures shall be taken so that the employee can be present in the space referred to in the first paragraph without hazard.
Put simply: the employee must not only be able to enter a confined space safely, but must also remain safe there while working. So for work in a confined space, two things have to be measured.
- Before anyone goes in, he or she must carry out a clearance measurement with a gas detector fitted with a pump. Air is drawn in through a hose for several minutes before anyone enters. It is very important to measure at different heights, because gas can be heavier or lighter than air.
- Once the space has been cleared, the person concerned can go in. For this there are smaller personal gas detectors that can be worn on the chest.
All those rules are fine, but what does it look like in practice?
In the vast majority of the cases we come across, a 4-gas detector is sufficient.It contains sensors for oxygen (O2), explosive gases (LEL), hydrogen sulphide (H2S) and carbon monoxide (CO). Depending on the situation, CO2, PID, NH3 or other sensors are added as well. The regulations name the following hazards:
- Asphyxiation
In practice this usually concerns a lack of oxygen. Is there a chance in your situation that the oxygen is displaced by another gas? Or a chance of a chemical reaction such as rusting, fermenting, rotting, curing of adhesives/paints, etc. Then you cannot rule out a risk of asphyxiation and measurements will have to be taken. - Narcosis
This concerns gases that can make you lose consciousness and fall asleep. Carbon dioxide, for example. Do you have to enter a space where CO2 pipes run to a cooling installation? Then you must measure this before you go in. - Poisoning
Examples of commonly occurring toxic gases are carbon monoxide and hydrogen sulphide. CO is released during incomplete combustion (yellow flame) or, for example, by ageing engines in installations or vehicles. H2S is a decomposition gas and is simply released whenever something is rotting. Waste water in sewers, manure or other organic waste, for instance. - Fire or explosion
The most common gas in nature that can cause fire or explosion is CH4, or methane. In many cases it occurs together with H2S, because CH4 is a decomposition gas too. But CH4 also comes out of the gas pipe at home. This is measured with an LEL sensor.
But an LEL sensor does not only measure methane. Depending on the type of sensor, they often also measure propane, butane, hydrogen, pentane, octane and a number of other substances.
BaSystemen has several suitable solutions for confined spaces. Popular instruments are the MultiRAE Lite, GMI PS200 and Blackline G7c Pump. Contact our specialists for advice that fits your situation.
