A disposable, self-contained, light weight integral device for detecting, by means of activating an indicator, the presence of a predetermined substance in a sample fluid which is introduced into a test chamber. The device has a deformable housing which forms a test chamber for interacting the indicator material with the sample fluid, wherein a rupturable vessel of reagent is contained adjacent the test chamber, which vessel can be ruptured by application of a predetermined pressure through the walls of the deformable housing. Upon rupturing the vessel, the contents thereof are exposed to the sample fluid introduced into the chamber. In the presence of the predetermined substance in the sample fluid, the indicator undergoes the indicated change. The device can contain more than one vessel and a receptacle. One or more of the vessels can contain more than one indicator substance.