Avoiding toxic gases from the pellet bunker
Making storage rooms for wood pellets safe by taking suitable measures
Wood pellets for heating systems and heaters are regarded as sustainable carbon dioxide-neutral fuel. However, the wood shavings pressed into oblong little sticks have potentially hazardous properties when stored in large quantities: the manufacturing process involving cutting up, heating and drying of the wood and the shavings gives rise to auto-oxidation processes in certain wood components. For example, gases are formed from unsaturated fatty acids, such as the harmful carbon monoxide (CO) and various aldehydes. Even months after production, the pellets can still emit gases. In storage rooms, the concentration can be so high that it can lead to severe poisoning in persons entering the rooms. “Many house owners and operators of heating systems fuelled with pellets are unaware of this hazard potential”, says Professor Dr. Dr. Andreas Hensel, President of the Federal Institute for Risk Assessment (BfR). “According to experimental studies, concentrations of up to several thousand ppm carbon monoxide can be reached inside pellet storage rooms which is sufficient for lethal poisoning.” How high the concentration is in a given storage room depends on the quantity stored, the temperature, ventilation and the age of the pellets.
Several human cases of carbon monoxide poisoning including lethal ones have been reported to the BfR. The persons had spent time in wood pellet storage rooms, so-called pellet bunkers, or they wanted to enter such rooms to carry out maintenance works. These storage areas were airtight, meaning that extremely high concentrations of carbon monoxide had accumulated in the rooms without being noticed by the casualties.
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