Are wood-chips the new jam-jars?

Regular readers of this web log will be more than aware of what Frank recently described as the ‘Great Jam-Jar Mystery’ and the legality, or not, of the re-use of jam-jars for the sale of conserves, pickles, &c at church fêtes and similar occasions.  In that case, the issue at stake was not a change in EU food hygiene legislation, but its interpretation nationally and locally in the UK.  This was the topic of widespread media interest, most of which served to confuse the situation rather than clarify it.

On 5th November, the Health and Safety Executive issued a Safety Notice ‘Risk of carbon monoxide release during the storage of wood pellets’ for the attention of

  • ■ Users/ installers/ maintainers/ distributors of wood pellet boilers; and

  • ■ Manufacturers/ storers/ distributors of wood pellets.

The reason church and faith groups should take heed of this advice is that the installation of wood pellet boilers is one of the potential options for meeting their energy reduction targets, such as in the Church of England’s Shrinking the Footprint Campaign.  The Diocese of Exeter is currently considering wood-burning boiler for church heating in addition to: installation of solar photo-voltaics at parsonages; churches as a source of solar power generation; air-source heating of vicarages; wind energy generation on glebe land; and managing church-owned woodland for biomass production; plus the long-term possibility of an anaerobic digester on diocesan glebe land.

Information on their installation and use is included on the Eco-Congregation site, but this does not currently identify these specific risks recently identified by the HSE.

Although there have been no reported fatalities in the UK, HSE notes that since 2002 there have been at least nine fatalities in Europe caused by carbon monoxide poisoning following entry of persons into wood pellet storage areas.  Three relating to domestic property have occurred since 2010, and wood pellet boilers are increasingly being considered as an alternative to oil or gas fired boilers in homes and businesses, and for the replacement of coal-fired boilers, particularly in schools.

Carbon monoxide is particularly dangerous since it is a colourless, odourless and tasteless gas that is highly toxic. When it enters the body, it prevents the blood from bringing oxygen to cells, tissues, and organs, and can kill quickly without warning.  The public is becoming increasingly aware of the need for carbon monoxide alarms any home using gas appliances, but the risks associated with wood chips/biomass are not generally appreciated.

The HSE Safety Note reports ‘experimentation has shown that small quantities of wood pellets can produce life-threatening quantities of carbon monoxide in a confined space and that there are various factors that will affect the amount of carbon monoxide produced:

  • Age: pellets will produce more carbon monoxide within the first six weeks of being manufactured.
  • Temperature: more carbon monoxide is produced at higher temperatures.
  • Wood type: pellets made from pine contain more unsaturated fatty acids than spruce so produce more carbon monoxide.
  • Other factors: carbon monoxide levels will also increase with the amount of available oxygen present, exposed pellet surface area and amount of mechanical abrasion of the pellets that has taken place.


Wood-chips are not the new jam-jars.  The Health and Safety Executive has issued an unambiguous warning of the risks associated with the operation of wood-chip heating facilities, and guidance on minimizing these risk for the groups that are likely to be involved.  The Safety Note identifies the groups who should take note of this advice.

Duty holders under Health and Safety at Work etc. Act 1974, c.37 are subject to certain legal obligation and sanctions.  For others, the detail in the Notice provides a component what might be construed as being  ‘reasonable foreseeable’ in the tort of negligence.

The major importance of the Notice, however, is its identification of the potential risks involved and the measures that must be taken to prevent future incidents.  The clear guidance given by HSE on this and other important issues, and its ready debunking of ‘health and safety myths’ provide an example that other competent authorites would do well to follow.