As writer Samuel Levenson best put it: “You must learn from the mistakes of others. You can’t possibly live long enough to make them all yourself.”
In this article, Andrew Watson delves into the bag of bad luck, bad management and bad practice he’s witnessed over the years to share what he’s learnt about gas detection and confined space safety – so you don’t have to find out the hard way.
Underground mine fire
An underground fire developed suddenly in a coal mine putting the mineworkers in a coal face district in serious danger. The mineworkers were travelling to safety through smoke and carbon monoxide wearing respiratory protection devices – filter self-rescuers. The first rescue team on site had a choice: go to the fire and extinguish it or head for the district and assist the mineworkers.
The decision was taken to fight the fire and attempt to clear the smoke and carbon monoxide from the mine environment to ease and speed up the mineworkers’ travels to safety.
A fresh air base was established as close to the fire site as possible. All equipment was checked and found to be in order. The team was deployed towards the fire. The route included crawling for several hundred metres before walking conditions improved and the team could stand and walk. On arrival at the fire site the team was met with a large, fierce fire. The ignition source was unknow as well as what had initially caught fire. The levels of carbon monoxide indicated on the mine’s fixed monitoring system was confusing due to the very sudden and rapid increase. The team began fighting the fire. The atmosphere was checked and immediately a problem was detected – the methane levels were indicated as being plus five percent. The methanometer detected zero to five percent. Since methane is explosive in the range of five to 15 percent, under these circumstances the decision was taken for the team to return to the fresh air base.
Before retreating the team set up a fire monitor (a fixed-point spraying water towards the fire). This was more to do with reducing smoke than fighting the fire. While travelling to the fresh air base it was noted that the methanometer continued to show plus five percent. It was recognised that this could not be correct. On returning to the fresh air base the team compared the reading with the environmental monitor located there that indicated fresh air. The teams methanometer still showed plus five percent methane. The team returned to the fire area. On arrival it was noted that the main fire was now extinguished, and the mine environment was considerably clearer of smoke. The carbon monoxide levels had reduced. The fire fighting monitor (the good luck) had been set up pointing at a pile of paper bags stored in the area (bad practice). The burning of these explained the sudden rise in levels of smoke and carbon monoxide.
The ignition source was a faulty electrical panel. The rapid increase in smoke and carbon monoxide was explained by the paper bags being stored near the electrical panel catching fire and spreading rapidly.
The mineworkers all escaped to safety.
The fire took another two days to completely extinguish as the coal behind the supports had caught fire.
The methanometer had been damaged, probably during the crawl, and from then on constantly indicated a full-scale reading. To learn from this to stop a repeat of this in future, all environmental equipment available to rescue teams should be backed up.
A mine was sealing off a salvaged coal district. This was work that was routinely carried out, as not to seal salvaged districts off timeously normally resulted in a spontaneous heating (fire) of the coal remaining in the district. The mine did not prioritise the sealing off, preferring to concentrate on coal production. Good practice was not being followed in that the seals being constructed did not include access tubes. The reason for access tubes being installed in a mine seal is twofold: firstly, to maintain constant ventilation until the seal is complete; secondly to allow access to the rear of the seal to ensure the quality of the seal. By not utilising the access tube the mine could not ensure a minimum quantity of air round the district to be sealed. As the seal neared completion, the amount of air being circulated around the district would reduce to an unacceptable level.
The above situation was exasperated by the mine, removing the fixed environmental monitoring from the district leaving only one sensor in the area. They had a sharp fall in atmospheric pressure which allows mine gases including methane to enter the mines main ventilation circuit. This additional gas is normally absorbed into the mine ventilation circuit and controlled at acceptable levels. They had a small spontaneous combustion in the district, which was the ignition’s source.
Due to the above situation of increased methane levels, reduced uncontrolled ventilation and an ignition source the inevitable happened. They had an explosion.
Fortunately, there were no people working in the area. The effect of the explosion was to damage the seals (which increased the volume of ventilation) but worse than that the levels of carbon monoxide produced by the explosion poisoned the fixed environmental sensors not only in the immediate area but also elsewhere underground. This meant that the mine had lost its source of information regarding environmental conditions.
The solution was to deploy a rescue team to take and communicate environmental reading using hand held instruments. They were to monitor carbon monoxide and methane levels.
As is good practice, two teams of five rescue operatives were deployed underground: one team to provide back up and rescue cover; the other team to take the readings.
The team deployed to take the readings were in the process of communicating their initial findings when they heard a second explosion heading in their direction. They protected themselves as best they could, but the force was sufficient to knock them over. They were lucky that this was a small methane explosion. The mine had taken the necessary precautions to ensure the coal dust was inert by mixing it with stone dust, thus preventing a much larger and more powerful coal dust explosion.
Everyone in the mine returned to the surface safely but shaken. The mine was eventually re-entered when the atmospheric pressure increased pushing gases out of the mine environment. The seals were completed properly, and the district sealed.
It is a pity good practice was not followed from the start.
Falsifying records and results
A coal mine in Russia was one of the first in that country to install a UK manufactured fixed gas monitoring system. The mine management realised that the system was so efficient that it reduced the time they had to mine coal. They thought they would be clever and trick the system to allow them to continue mining while reducing the safety margins that the system would provide and indicate. A mining engineer from the UK was at the mine monitoring the system when he realised something was not right. He went underground to investigate and unfortunately was caught in an explosion and killed.
The mine management was taken to court and based their defence on the new (UK) monitoring system not providing the results required to allow them to mine safely. They produced a set of false records to prove their point.
The UK based company was called as witnesses for the prosecution. Unknown to the mine management, the monitoring system maintained a back up set of records which indicated the true environmental results from the mine.
These results proved that the mine had blocked sensors underground to prevent the system alarming and cutting off electrical power underground.
Due to the evidence provided by the backup system the mine management were successfully prosecuted. The UK based company still operate in Russia and they and their monitoring system are held in the highest regard.
It is ridiculous that people lost their lives by production being put before safety. If the job cannot be done safely then do not do the job.
One of the most unusual requests I have been involved in was to travel out to sea and test a ship hold full of coal for a spontaneous combustion. The ship was due to dock in the UK. Prior to being allowed to dock the ship was required to send an environmental report to the port to ensure there was no risk of the coal having spontaneously combusted during transport. The reading sent from the ship indicated a high level of carbon monoxide. Carbon monoxide being produced by incomplete combustion is an indication of spontaneous combustion.
The trip involved travelling out to sea in a pilot boat and being scooped into a net and lifted aboard the massive boat.
There was no spontaneous combustion. There was, however, an out of calibration environmental monitor with faulty sensors. This cost the shipping company a lot of time (money) and unnecessary stress.
“prior to being allowed to dock, the ship was required to send an environmental report to the port to ensure there was no risk of the coal having spontaneously combusted during transport”
Aviation fuel tank cleaning
A worker was deployed to clean an aviation fuel tank that had just been manufactured. The worker was using chemicals to clean the tank. No environmental monitoring was carried out. The work inside the tank was so hot that the worker went to unplug his inspection lamp to reduce the heat levels. The spark produced when he unplugged the lamp ignited the chemicals being used to clean the tank causing an explosion in a confined space.
The worker was left with life changing injuries. He is confined to a wheel chair and will never work again.
The company was successfully prosecuted for not having properly carried out an assessment of the risks involved and for not introducing the required control measures to reduce the foreseeable risk to an acceptable level.
Worse than that, it was concluded that the chemicals that ignited were of no use as a cleaning agent at all – soapy water would have been as good.
This leads me onto good practice. The best method I can suggest is to follow the Health and Safety Executive’s guide on how to carry out and develop a risk assessment:
- Step 1: Identify the hazard
- Step 2: Decide who might be harmed and how
- Step 3:Evaluate the risk and decide on the precautions
- Step 4: Record your findings and implement them
- Step 5: Review your assessment and update if necessary
Identify the hazard
It is important to remember that the hazards to be monitored can either present naturally or imported/ produced. Examples of naturally occurring hazards are spontaneous combustion (e.g. coal or grease) or rusting absorbing oxygen in a confined space. Examples of imported or produced hazards would be welding to carry out a repair in a confined space, the use of cleaning chemicals or the production of oxygen or nitrogen etc.
The most likely hazards are outlined below:
- Flammable substances
- Oxygen enrichment
- Toxic gas
- Oxygen deficiency
- Airborne dust
It should also be remembered that the hazard can either affect the worker by inhalation or by absorption.
There is the risk of a fire or explosion where flammable substances are present. This can be exasperated by the presence of an oxygen rich environment, which could lower the flammability range of a substance. The enriched oxygen coming from the production of oxygen or leaking from an oxygen system (hospital) or from an oxygen cylinder used for welding or breathing apparatus.
The toxic gas, fume or vapour may be present from a process or from storage of a substance. It is important when testing a storage or process area that contains sludge or other deposits to safely disturb it to release any fumes trapped there into the atmosphere to allow an accurate assessment of the risk to be carried out.
“everyone working in a hazardous environment – whether ensuring it is safe and healthy, doing the work or available for rescue – should be competent to do so”
Oxygen deficiency can be present from many sources, such as:
- Naturally occurring due to biological processes absorbing oxygen. These can be present in sewers, storage tanks, storm water drains and wells. It is also possible for an oxygen deficient atmosphere to be produced during fermentation in silos. This is also possible in ship holds transporting wood, metal that rusts, vegetables, grain and of course coal.
- Vessels that can rust as the process of rusting is a slow form of combustion that uses oxygen. This can occur in newly manufactured vessels especially in ones that have been shot blasted.
- Limestone chippings, when wet, produce carbon dioxide which replaces oxygen.
- During pipe freezing using, for example, liquid nitrogen.
- Workers breathing in a confined space without adequate ventilation.
- Purging a confined space with an inert gas to remove a flammable or toxic gas, vapour or fume.
It is very important not to forget to monitor the environment for airborne dusts. Dusts such as coal, flour and plastic (and many others) can ignite if lifted into the air. In coal mining the largest loss of life has always been associated with coal dust explosions. A methane explosion lifts coal dust into the air and the dust ignites spreading the explosion over a very large area, usually increasing in force as it travels.
Who can forget the Bosley Mill dust explosion in 2015 which cost four lives.
The environment should be monitored for excessive heat. Workers are at risk of heat exhaustion and heat stroke when exposed to heat. This can be in areas around industrial ovens or in paper mill drying rollers. In mines, precautions commence from temperatures above 22 degrees Celsius. It is also important to be aware that you do not acclimatise to heat. As soon as you are removed from the heat for a short period of time, i.e. a weekend or a break you lose any acclimatisation you had. Therefore, workers should be introduced to hot work areas gradually. Other precautions are regular sips of cool water and eating complex food such as Christmas or mint cake, as used by hill walkers and mountaineers.
It is important to consider work affecting other remote areas. An example of this being a leaking propane cylinder used for welding. Propane is much lighter than air (specific gravity) and leaking propane will rise accumulating in areas above the work area. This can be a considerable distance from the work area. The opposite of this would be leaking carbon dioxide cylinders.
These are used for example in pub cellars which are due to carbon dioxide being much heavier than air and collecting in the lowest part of the cellar.
Who might be harmed?
This will be those working in the area. Do not forget those affected in the event of a fire or explosion or visitors (authorised or not). Also remember rescue team members if they are required to remedy a problem.
Evaluate the risk and the precautions (or control measures)
When evaluating the risk consider the potential harm from the hazard, i.e. minor injury, serious injury or death. Take into account the history of events and incidents taking place and estimate the likelihood of harm coming from the hazard.
- Know what you are testing for – hazard, effect, specific gravity etc
- Check if a control of substance harmful to health assessment is required and if so if it is available
- Know the history
- Ensure the environmental monitoring device whether fixed or hand held is fit for purpose, maintained and calibrated
- Define where and when environmental testing will be carried out – initial, during and following entry
- If anything changes, i.e. work or atmosphere, then re-assess
- Know why and what could change within the environment
- Ensure the competence of workers
- Ensure competence of those testing the environment
- Ensure the environmental readings taken are correctly interpreted and understood
- If the readings are unusual or not as expected, re-assess
- Make arrangements for rescue
Now revisit your risk assessment and re-evaluate the likelihood with the precautions or control measures in place.
Remember the potential harm from the hazard will be unchanged; it is the likelihood of an incident happening that will have reduced due to the implementation of precautions or control measures.
Keep a record (documents) of your risk assessments and a continuous accurate log of environmental monitoring. These are your history and will be useful in the future or if anything untoward, unplanned or unforeseen occurs. It is helpful, where possible, to take and keep pictorial evidence of events, precautions and controls as they are being implemented.
Review and update
To ensure continuous improvement to safety and health – no matter how well the environmental monitoring and the work has gone – always continually review and update risk assessments and controls as necessary. This could be for better or updated environmental equipment becoming available or more efficient work processes or improved or new chemicals which would improve safety or environmental impact.
When working in a potentially hazardous atmosphere do not forget to plan for rescue and test out the systems and individuals involved regularly.
Everyone working in or potentially working in a hazardous environment – whether ensuring it is safe and healthy, doing the work or available for rescue – should be competent to do so.