Preface The standards set forth herein apply to the second edition of the Standard for Direct Gas-Fired Door Heaters, ANSI Z83.17- 1990, and Addenda thereto, Z83.17a-1991, and supersede corresponding standards therein. Following their preparation by the supervising subcommittee, they wee accepted by Accredited Standa rds Committee Z83 and subsequently approved as American National Standard by the American National Standards Institute, Inc. NOTE: Changes, other than edit