This test paper allows the quick and sensitive detection of blood traces. In criminal investigations it is used as a rapid screening test. 
The test paper uses the pseudo-peroxidatic effect of blood. The material in question is allowed to soak in water for about 1 minute. Then the test paper is pressed to the sample. Blood traces lead to a distinct discoloration within a few seconds. The test papers are single sealed in plastic. This ensures safe results at any time.