US Patent 3,419,029 Breathing Valve Assembly HH Straub Dec 31 1968 This appears to be simpler solution that can be AM'd quickly Also, medical staff prefer not to use face masks because if the mask does not fit well on…
US Patent 3,419,029 Breathing Valve Assembly HH Straub Dec 31 1968 This appears to be simpler solution that can be AM'd quickly Also, medical staff prefer not to use face masks because if the mask does not fit well on…