A method and device is disclosed for measuring one or more physical properties of, and/or induced by, out-gassing products released from and/or trapped within a joint in response to a lightning strike or other electrical current threat. A device for measuring one or more physical properties of, and/or induced by, gases, plasma and/or particles released from a joint in response to an electrical current threat. The joint includes a fastener passing through a structure so that an end of the fastener protrudes from the structure. The device includes a containment member having a base surrounding an opening into a cavity, the containment member being arranged to be mounted over the end of the fastener to enclose the end of the fastener within the cavity and to seal the opening; and one or more sensors arranged to measure physical properties of gases, plasma and/or particles contained by the cavity.