Adsorbent cartridge with accurate visual indicator

Abstract

A cartridge comprising layers of adsorbent sheet is described. The cartridge includes an indicator that characterizes the consumption state of the adsorbent within the cartridge. The indicator is applied in a way such that discrete areas of indicator are visible. These discontinuous areas of indicator may be applied to the outside surface of the cartridge. Alternatively, the discontinuous areas may be formed by cutting windows in the outermost layer of the cartridge and either coating indicator on the layer beneath the window, placing an indicator layer between the window and the layer beneath it or filling the window with an indicating plug of material so that the indicator is visible from the outside of the cartridge. The indicator layer and indicator plug embodiments allow the use of any indicator with any adsorbent.

What is claimed is: 
     
         1 . An adsorbent cartridge for removing gaseous contaminants, comprising layers of one or more self-supporting adsorbent sheets mechanically spaced to provide gas flow channels between the layers from one end of the cartridge to the other, wherein the cartridge further comprises a color indicator for visually indicating consumption of the adsorbent to an external observer, wherein the color indicator is applied to one or more areas of an outermost layer of the adsorbent sheets of the adsorbent cartridge. 
     
     
         2 . The adsorbent cartridge of  claim 1 , wherein the cartridge is formed from a single self-supporting adsorbent sheet wound into a roll to form multiple layers. 
     
     
         3 . The adsorbent cartridge of  claim 1 , wherein the cartridge is formed from a stack of the self-supporting adsorbent sheets. 
     
     
         4 . The adsorbent cartridge of  claim 1 , wherein the sheet is formed from a mixture comprising an adsorbent material. 
     
     
         5 . The adsorbent cartridge of  claim 4 , wherein the sheet is formed from a mixture comprising polymer and the adsorbent material. 
     
     
         6 . The adsorbent cartridge of  claim 4 , wherein the adsorbent material comprises calcium hydroxide or lithium hydroxide. 
     
     
         7 . The adsorbent cartridge of  claim 1 , wherein the color indicator comprises ethyl violet, Titan yellow, Kenazol yellow, activated alumina with thymol blue, or o-cresolpthalein. 
     
     
         8 . The adsorbent cartridge of  claim 1 , wherein the total surface area of all color indicator in the cartridge is 0.05% to 50% of the surface area of the outermost layer. 
     
     
         9 . The adsorbent cartridge of  claim 1 , wherein the color indicator is applied to the outermost layer of the adsorbent sheets of the adsorbent cartridge by spraying the color indicator onto the outermost layer of the adsorbent sheets of the adsorbent cartridge. 
     
     
         10 . The adsorbent cartridge of  claim 1 , wherein the layers are mechanically spaced by parallel, longitudinal ribs molded out of the sheet. 
     
     
         11 . An anesthesia breathing circuit comprising the adsorbent cartridge of  claim 1 . 
     
     
         12 . An underwater breathing apparatus comprising the adsorbent cartridge of  claim 1 .