A simple and inexpensive radiation detection device has been constructed sensitive to gamma fluxes in the range from a few to a few hundred roentgen per hour. Thus one can distinguish between dangerous and relatively safe radiation levels such as one might expect from radiological warfare, low level atomic blasts, or from ``rigged'' hydrogen bomb explosions.A typical device consists of two gamma‐activated crystals in a light‐tight container which can be held close to one eye to exclude external light. A radium‐activated phosphorescent material is included for light intensity comparison purposes. The more sensitive crystal can be discerned in a gamma radiation of a few R/hr, and its light output matches that of the fluorescent material at levels of 20 to 30 R/hr. The light from the less sensitive crystal matches that of the phosphorescent material at about 100 R/hr.