A tool for severing a conduit includes a housing defining a void that encircles a conduit to be severed. There is at least one propellant source located within the housing. Upon ignition by an ignition mechanism, the propellant source deflagrates, creating at least one stream of combustion products. The combustion products flow out of the tool through at least one void access and into the void. The void access channels the combustion products towards the conduit. The stream of combustion products combines with a modifying material to sever or assist in severing the conduit. A method of severing a conduit using the tool is provided.