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Heat-responsive duct closing method and apparatus

  • US 3,990,464 A
  • Filed: 04/08/1975
  • Issued: 11/09/1976
  • Est. Priority Date: 04/08/1975
  • Status: Expired due to Term
First Claim
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1. The method of closing a heating and ventilating duct upon the occurrence of fire to prevent the flow of a gas through the duct, which comprises the steps of:

  • a. arranging within the duct an impervious inflatable bag in the collapsed condition;

    b. connecting the bag with normally de-activated bag inflating means; and

    c. activating said bag inflating means when the temperature of the fluid in said duct exceeds a given value to expand said bag to an expanded condition in sealed engagement with the entire inner circumference of a portion of the duct, thereby to prevent the flow of fluid through the duct.

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