Health issues with wooden pellets releasing carbon monoxide
The Churches Legislation Advisory Service have issued the following statement about wood pellets:
The Health and Safety Executive has issued a Safety Notice Risk of carbon monoxide release during the storage of wood pellets for the attention of users, installers, maintainers and distributors of wood-pellet boilers and of manufacturers, storers and distributors of wood pellets. 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 – so care is needed in storage.
Carbon monoxide is particularly dangerous since it is a colourless, odourless, tasteless and highly toxic – and can kill quickly without warning. Though people are becoming increasingly aware of the need for carbon monoxide alarms in any home using gas appliances, the risks associated with wood chips/biomass are not generally appreciated.
The HSE Safety Note reports that:
“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”.
Installing wood-pellet boilers is one of the potential options for meeting energy reduction targets, such as in the Church of England’s Shrinking the Footprint campaign. The Diocese of Exeter, for example, is currently considering wood-burning boiler for church heating in addition to such measures as installation of solar photo-voltaics at parsonage-houses, using churches as a source of solar power generation and managing church-owned woodland for biomass production. plus the long-term possibility of an anaerobic digester on diocesan glebe land.
[Source: HSE Safety Notice – 5 November 2012]
This risk is genuine but the HSE bulletin does not report the root cause (they simply offer a theory about auto-oxidation of the pellets). An alternative theory is that the boilers and flues were not installed correctly or need cleaning so that circulation or blow-back of flue gasses occurr through the pellet store and so it is flue gas CO that builds up.
To put this in perspective, there were 3 deaths across the whole of Europe from 2010 to now.
By comparison, there are typically 3000 deaths per year from road traffic accidents in the UK alone.
Guidance offered by HSE is:
- Wood pellet hoppers/tanks/storage rooms and boilers should always be installed and commissioned by a competent person, normally approved by the manufacturer/supplier. This is particularly important if the installation involves the replacement of a coal-fired boiler, where existing boiler room and storerooms are often utilised.
- Do not enter the pellet storage area or place your head into a wood pellet hopper as they can contain toxic gases. No personnel should enter the hopper/tank unless fully trained and competent in confined space entry procedures. Controls should be put in place to ensure safe entry as per the HSE’s Code of Practice for Working in Confined Spaces. This should include adequately ventilating the storage area and checking carbon monoxide and oxygen levels with an appropriate device prior to entry. It is recommended that the store room is ventilated at all times, either mechanically or by being designed to have a through draft.
- Ensure that the boiler and pellet feed mechanism etc. is cleaned and serviced by a competent person as specified by the manufacturers’ instructions.
- If any problems are encountered with the unit, such as the system not heating correctly or flue gas is flowing into the boiler room, turn the unit off and contact the supplier and/or manufacturer and request assistance.
- Duty holders who store wood pellets, particularly in bulk should have a suitable risk assessment and safe system of work in place.
- Manufacturers, suppliers and distributors of wood pellets should provide adequate health and safety information to the user in their materials safety data sheet.
- Warning signs should be placed on the pellet storage area access door, ideally on both sides so it can be seen when the door is open. The warning sign should include the following information:
- DANGER – RISK OF CARBON MONOXIDE POISONING – There is a danger to life from odourless carbon monoxide and lack of oxygen. Check atmosphere before entry with an appropriate device. No entry for unauthorised persons. Keep children away from the storeroom.
- No smoking, fires or naked flames.
- The room should be adequately ventilated before entering. Keep the door open whilst inside.
- There is a danger of injury from movable parts.
- Filling procedures should be carried out accordance to the instructions of the heating installation company and the pellet suppliers.
If you have any concern about your own pellet store I would suggest you get a Carbon Monoxide alarm in the first instance and leave it in the store to see what reading it gives. They are readily available from many hardware and other stores and cost less than £20.
Alternatively, give us a ring.