A flash arrestor applicable to suppress explosions in gas lines generally, but specifically appropriate for suppressing explosions of pyrophoric gases, particularly silane in connection with integrated circuit manufacturing, has two identical flash suppression assemblies that are interconnected and act bidirectionally so as to suppress explosions occurring on either side of the apparatus. In particular, the present invention provided improved substrates and methods of using liquid crystal assays for quantitating the amount of an analyte in a sample. A plurality of lug holes are formed in a central portion of the hub through which lug studs pass when a rear side of the central portion is mounted against an axle hub of a motor vehicle.