Exposure to carbon monoxide from wood pellets

Status:

completed 09/2016

Aims:

Carbon monoxide (CO) is released from wood pellets as a result of autoxidation. In inadequately ventilated storage rooms, the CO concentration may attain potentially fatal levels. This has led to fatal accidents in Europe in recent years. The aim of the Project 9179 within the Measurement System for Exposure Assessment (MGU) was to determine by measurement inhalative exposure of CO across the entire logistical chain in stores/silos at the premises of manufacturers, distributors and final customer.

Activities/Methods:

During the MGU measurement campaign 9179 examining CO from wood pellets, inhalative exposure to CO was studied across the entire delivery chain in stores and silos at the premises of manufacturers, distributers and final customers. Measurements were performed from 2014 to 2016 by the measurement services of the BGHM and BGHW, by means of the MGU Measurement System for Exposure Assessment of the German Social Accident Insurance Institutions. Altogether, over 250 measurements were taken at 26 sites.

Results:

The great majority of the measurements were performed at the premises of manufacturers and distributers. It was found that the measurement values several times the occupational exposure limit of 35 mg/m3 (up to 360 mg/m3 in outdoor silos, up to 1100 mg/m3 in indoor silos) may be anticipated in both empty and full or partly filled silos. This also applies to the part of the silo directly below open hatches. At the premises of wood pellet manufacturers, additional measurements were performed in the adjacent working areas such as elevator sumps and control rooms as well as in the silos themselves. The values measured in this case were consistently below the occupational exposure limits. At customers' premises, wood pellets are not only stored in silos; they are also stored in loose bulk. The measured values in this case were consistently in the non-critical range below one-tenth of the occupational exposure limit. Violations of the occupational exposure limit were also measured in wood pellet stores at the premises of final customers. Maintenance personnel such as caretakers, heating installation technicians and electricians are particularly affected in this case. In addition, in the event of faults in function or poor maintenance of the heating installation, return flows of flue gas into storage rooms may result in a considerable additional CO input.

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