Abstract: The present invention is with respect to a reflectance measuring head that is designed for stopping the production of false readings by regular (as opposed to diffuse) reflection and shiny parts of the sample without using normal shine traps or diaphragms. False readings as produced by regular reflection, by surface grain or structure and by inhomogeneity of the surface of the sample are furthermore put an end to by having a number of transmitters placed at an equal distance from one receiver or having a number of receivers placed at an equal distance from a transmitter. A more specially useful effect is produced if a number of transmitters and a number of receivers are placed alternately in the form of a matrix.

Abstract: A method for monitoring the exposure of an individual person to toxic gases is carried out such that the gas concentration is continuously measured with a sensor for the specific gas, recorded and the measured values then read and evaluated. Instantaneous values of the concentration are periodically scanned, temporal mean values of the instanteous values are formed over a predetermined time interval, these mean values are stored and an alarm triggered if the instantaneous value and/or the mean value exceeds a predetermined critical value over the time interval or an integral multiple thereof.