Abstract: A helmet formed of a rigid shell is disclosed. The shell is lined with several air filled bladders to contact firmly the head of a user. The shell has a rigid chin bar supporting a bite bar connected fixedly to a mouthpiece bearing against the teeth and hard palate to firmly anchor the helmet without movement. The outer shell surface supports various air pumping bulbs and accelerometers. Separate left and right visor pivot on the side guided in a central tongue and groove track to move optical lens mounts into the user's field of vision. The chin bar is connected to the shell by a pair of releasable clasps. A safety lanyard connects to the clasps to quickly pull pins from the clasps to enable quick release in case of motion sickness.

Abstract: The disclosure is of an assembly for determining light transmissiveness of a fluid. The assembly comprises a light source, means of holding the fluid in a light-shielded path of the light generated and a means for receiving and measuring the attenuated light passed through the fluid sample. The assembly is simple and highly portable. As such it is convenient for use with little training in places such as a physician's office, for measuring substances in immunoassay reaction mixtures.