Exposure indicator with continuous alarm signal indicating multiple conditions
 An exposure indicating apparatus and indicating method includes a sensor having a property responsive to a concentration of a target species. A processing device generates a concentration signal as a function of the property and an indicator is activated as a function of the concentration signal. The indicator is activated at a signaling rate indicative of an exposure indicating apparatus operating within predefined design parameters and at an exposure signaling rate indicative of the concentration attaining a predetermined threshold concentration. The indicator may also be activated at a signaling rate indicative of an exposure indicating apparatus operating outside of the predefined design parameters, and after the predetermined threshold concentration is attained, the indicator may be activated at an exposure signaling rate which varies as a function of the concentration signal. 
Minnesota Mining and Manufacturing Company
A
A62B
inventional
Lowell R. Mark K. Edward E. Richard J. Gregory
Miller Debe Parsonage Poirier Yuschak