Flow resistance of the C4 inlet and outlet valves – Design of a valve production quality control apparatus, and comparison with evaluation on a headform


  1. Bodurtha, P.
  2. Hoedlmoser, K.
  3. Compeau, S.
  4. Dickson, E.F.G.
Corporate Authors
Defence Research and Development Canada, Kingston Ont (CAN) Defence and Security Research Institute
The C4 respirator is an air purifying respirator designed for and worn by the Canadian military. In 2008, the manufacturer of the respirator, requested a specification change for the inlet nosecup valve that would potentially alter its permissible breathing resistance characteristics, and Director Soldier Systems Programme Management requested that the Royal Military College of Canada (RMCC) Chemical-Biological-Radiological-Nuclear (CBRN) Protection Group (CPG) evaluate the impact of this potential change. As an outcome of this previous work, CPG developed an updated benchtop apparatus to be used for production quality control purposes, and an additional replicate apparatus was constructed to remain with the Crown at RMCC for future quality control and design purposes. An additional Crown apparatus based on a headform was devised in order to measure respirator pressure drops in situ, so as to have a record of the actual performance of the various components of the entire respirator system, including those that the benchtop apparatus was not able to evaluate. The following observations and recommendations were made as a result of this study: (i) the redesigned Crown 2 apparatus is suitable as a quality control apparatus for production use; (ii) regular flow calibration of the apparatus should be performed; (iii) the inlet and outlet valve specifications should be rewritten to conform to the new method and apparatus; (iv) the specification for the nosecup valve should be rewrit

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Report Number
DRDC-DSRI-TM-2009-011 — Technical Memorandum
Date of publication
01 Dec 2010
Number of Pages
Electronic Document(PDF)

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