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Background: During the 2003 war in Iraq, Israel faced the problem of supplying biological/chemical respiratory protection for a population in need of ventilator support. The devices in use were insufficient in terms of protective value, costs, and availability. An adaptor was developed to allow connection between respirators and the standard biological/chemical filter canister., Objective: As part of the safety protocol for such a device, an investigation was made to determine the possibility of combustion of the biological/chemical filter canister, because of a possible exothermic reaction between the inspired oxygen-enriched air flow passing through the canister and the activated charcoal component of the filter., Methods: A mechanical ventilator generated airflow with a frequency of 24 breaths per minute and a 500-mL tidal volume, for 90 minutes, through 14 standard filter canisters in a sealed chamber at a temperature of 25 degrees C and through seven canisters at a temperature of 30 degrees C. Incremental levels of oxygen (21-100%) were used for each set of canisters. The temperature of each filter was recorded throughout the examination., Results: There was no elevation in the final temperature of the filters after 90 minutes of airflow with high oxygen levels. There were no signs of ignition., Conclusion: High oxygen levels passing through the activated carbon in the filter canister placed between the mechanical ventilator and the patient do not cause a combustion reaction, making it a safe means for respiratory protection for patients undergoing mechanical ventilation.