Preface This is the second edition of ANSI Z21.66 / CSA 6.14, Automatic damper devices for use with gas-fired appliances . It supersedes the previous editions published in 1996. Scope 1.1 This Standard applies to the construction, performance, and installation procedures for a newly produced automatic damper device (hereinafter referred to as device) constructed entirely of new, unused parts and materials and designed to control the flow or products of combustion from an individually, automatically operated, gas-fired appliance listed by a nationally recognized testing agency. This device is not for installation on any appliance converted from solid or liquid fuels. This Standard also applies to automatic outdoor vent dampers intended to be mounted outdoors on the top of fireplace chimneys and do not apply to service chimneys or common vents used for venting central heater or water heating appliances. Automatic outdoor vent dampers areintended to be mounted outdoors only on the top of fireplace chimneys and used with decorative fireplace appliances, certified to the Standard for Decorative gas appliances for installation in solid fuel burning fireplaces, ANSI Z21.60 / CSA 2.26, or to the Standard for Manually lighted, natural gas decorative gas appliances for installation in solid-fuel burning appliances, ANSI Z21.84. 1.2 This Standard does not apply to a flue damper, which is a device installed before (upstream of) the draft hood relief opening(s). 1.3 A device covered by this Standard has an inlet and outlet venting area each no greater than that of a vent connector having a nominal 12 inch (305 mm) diameter [113 square inches (729 cm2)]. Outdoor automatic vent dampers intended to be mounted outdoors on the top of the fireplace chimney has an inlet and outlet venting area each no greater than that of a vent connector having a nominal 24 inch (610 mm) diameter. 1.4 Additional provisions specific to electrically operated automatic vent damper devices are outlined under Clause 6. 1.5 Additional provisions specific to thermally actuated automatic vent damper devices are outlined under Clause 8. 1.6 Additional provisions specific to retrofit automatic vent damper devices are outlined under Clause 10 (see Exclusion - Clause 10). 1.7 If a value for measurement as given in this Standard is followed by an equivalent value in other units, the first stated value is to be regarded as the specification. 1.8 All references to \"psi\" throughout this Standard are to be considered gage pressures unless otherwise specified. 1.9 Clause 13 contains provisions that are unique to the United States. 1.10 Clause 14 contains provisions that are unique to Canada. 1.11 Clause 2 contains a list of standards specifically referenced in this Standard and sources from which these reference standards may be obtained. 1.12 The following requirements apply to automatic vent dampers intended to be mounted outdoors on the top of fireplace chimneys and do not apply to chimneys used for venting central heating or water heating appliances. Each fireplace operates with only a gas log set or a vented decorative gas appliance whose only function lies in the esthetic effects of the flames: a) Devices covered by these requirements are capable of operation at ambient temperature of 32 to 130 °F (0 to 54.4 °C). They are also capable of operation at lower or higher temperatures when so specified by the manufacturer. b) For installation in a vertical position only. c) The vent damper may be used in conjunction with a vent cap listed for use on fireplace chimneys. 1.13 In this Standard, \"shall\" is used to express a requirement, i.e., a provision that the user shall satisfy in order to comply with the standard; \"should\" is used to express a recommendation or that which is advised but not required; and \"may\" is used to express an option or that which is permissible within the limits of the standard. Notes accompanying clauses do not include requirements or alternative requirements; the purpose of a note accompanying a clause is to separate from the text explanatory or informative material. Notes to tables and figures are considered part of the table or figure and may be written as requirements. Annexes are designated normative (mandatory) or informative (non-mandatory) to define their application.