Patent ID: 7947109

Claim:
A powered air purifying respirator capable of directing a forced flow of air to a wearer, comprising: a member having an air flow path for said forced flow of air; a fan, fluidly coupled with said air flow path, creating said forced flow of air; a filter disposed in said air flow path; a battery, operatively powering said fan, exhibiting, in some circumstances, passivation; an electronic control processor including at least a voltage delay sensing circuit and a correction circuit; and a signal, operatively coupled to said voltage delay sensing circuit, providing a first indication to a user of said passivation of said battery; wherein the voltage delay sensing circuit is operatively coupled to the battery and the correction circuit is operatively coupled to said voltage delay sensing circuit and to said battery, overcoming said passivation of said battery responsive to said voltage delay sensing circuit by limiting current drawn from said battery; wherein the signal further provides a second indication to the user based on a current level available from said battery when the powered air purifying respirator achieves a minimum flow rate of said forced flow of air.