Farm worker exposed to toxic gases

Prosecution following farm worker’s exposure to toxic gases

Key Facts:

  • A farm owner and his two businesses have been fined following as a result of serious safety failings
  • A worker, 29, died as a result of exposure to toxic hydrogen sulphide gas
  • The HSE found a number of unsafe practices and failings
  • The owner and his two businesses were fined £15,000, £45,000 and £10,000 and were ordered to share £75,000 in costs

The case:

The case, heard at Dorchester Crown Court on 23 February 2015, was told how two workers (MP and DB) were exposed to toxic gases whilst working on a farm in Bechalwell.

MP and DB were carrying out maintenance of an anaerobic digestion (AD) plant at the farm. A stirring mechanism in the AD tank had stopped moving after a crust formed in the tank. After opening the roof of the tank, they were engulfed by toxic hydrogen sulphide gas.

As a result, the two men lost consciousness. When DB regained consciousness, he was unable to get a response from MP, and he alerted other farmworkers on an ambulance was called. MP was declared dead without having regained consciousness. Two paramedics and two other farmworkers were also affected by the toxic fumes.

The roof had been opened on four previous occasions. Had the plant been operating correctly, this should only have been required rarely.

A number of unsafe practices and failings were found by the HSE during both the construction and the operation of the AD plant:

  • The risks of the plant in general were not assessed, nor were the risks of opening the roof.
  • Workers were not trained to remove the roof, nor was it recognised that this was a specialist job.
  • Risks, which include explosion and exposure to toxic gases, were poorly understood
  • The removal of the roof required work at height, and this was also carried out without adequate safety precautions.

On 1 August 2008, a similar incident had taken place, but this was not reported to the HSE. Here, another worker (JG) had fallen unconscious after being exposed to the toxic gases whilst carrying out maintenance on the roof. Following this incident masks were supplied, but workers were never trained in how to use them, they were not properly maintained or face-fitted, and were taken off once the roof had been removed under the mistaken belief that the danger had passed.

The farm owner was fined £15,000 after pleading guilty to two breaches of the Health and Safety at Work etc Act 1974. He also pleaded guilty to two further breaches as a partner in another business and was fined £45,000. His third company was fined £10,000 after pleading guilty to breaching section 42 of the Health and Safety at Work etc Act 1974. The owner and his company were ordered to share £75,000 in costs.

What is Anaerobic Digestion (AD):

The AD plant included a digester tank inside which cow slurry, agricultural waste and energy crops are heated and mixed by agitators. AD installations can also capture biogas from household food waste, garden waste, and waste from food processing factories. AD uses natural bacteria in the absence of oxygen in order to convert this organic matter into biogas, and a residue known as digestate.

Biogas is rich in methane and contains carbon dioxide, as well as the highly toxic hydrogen sulphide. This biogas is then stored in a gas holder on the roof of the AD plant before being used to generate electricity.

The major health risk associated with biogas is exposure to hazardous substances. Methane and carbon dioxide are both asphyxiating gases. They have the potential to cause fatal accidents by depleting the oxygen supply in closed or confined spaces. Hydrogen sulphide is a very aggressive, toxic bi-product, and short term single exposure can cause rapid unconsciousness and death.

The major physical risk associated with biogas is its flammability. There is a risk of fire and explosion if the gas mixes with air.

What the HSE Inspector had to say:

Speaking after the hearing, the HSE Inspector Annette Walker stated that:

The previous incident involving Mr Grondke should have served as a warning about the risk of toxic substances when opening the roof. If that risk had been identified and safe systems of work put in place to prevent exposure to workers, the tragic death of Matthew Pitt would have been avoided.

While farm energy generation from anaerobic digestion is an emerging application in the UK, anaerobic digestion has been used here for several decades for treatment of sludge by water companies.

The risks associated with access to confined spaces and the associated potential for exposure to hydrogen sulphide in anaerobic digestion facilities are well-known.

What has happened at that farm demonstrates the importance of having safe systems of work in place, particularly for maintenance and repair work where the risk of exposure is likely to be highest. The need for specialist skills and training also has to be recognised.

What the law states:

Section 2(1) of the Health and Safety at Work etc Act 1974 states: “It shall be the duty of every employer to ensure, so far as is reasonably practicable, the health, safety and welfare at work of all his employees.”

Section 3(1) of the Health and Safety at Work etc Act 1974 states: “It shall be the duty of every employer to conduct his undertaking in such a way as to ensure, so far as is reasonably practicable, that persons not in his employment who may be affected thereby are not thereby exposed to risks to their health or safety.”

Section 4(2) of the Health and Safety at Work etc Act 1974 states: It shall be the duty of each person who has, to any extent, control of premises to which this section applies or of the means of access thereto or egress therefrom or of any plant or substance in such premises to take such measures as it is reasonable for a person in his position to take to ensure, so far as is reasonably practicable, that the premises, all means of access thereto or egress therefrom available for use by persons using the premises, and any plant or substance in the premises or, as the case may be, provided for use there, is or are safe and without risks to health.

Section 37 of the Health and Safety at Work etc Act 1974 states: “Where an offence under any of the relevant statutory provisions committed by a body corporate is proved to have been committed with the consent or connivance of, or to have been attributable to any neglect on the part of, any director, manager, secretary or other similar officer of the body corporate or a person who was purporting to act in any such capacity, he as well as the body corporate shall be guilty of that offence and shall be liable to be proceeded against and punished accordingly.”

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