Under battlefield conditions a sensor that would present the soldier with an unequivocal indicator of the life remaining in his cw filter is an urgent requirement. It must be dependable, simple interpret and have no unusual power requirement. It should be inexpensive enough to dispose away with the exhausted filter, yet have long shelf life. The colorimetric sensing mechanism developed in this program meets these properties. It is interference free, with respect to most common pollutants such as motor exhausts and most industrial pollutants. It will not deteriorate in the presence of filter materials such as asc whetlerite and the color change will not be impeded or obscured by it.
