Risk of carbon monoxide release during the storage of wood pellets

The HSE is advising all those who use, install, maintain or distribute wood pellet boilers and/or manufacture/store/distribute wood pellets to consider the following:

• 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 Spaces⁵. 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.

For more information, see the HSE website.