1.1 Scope
This Code applies to the methods for classification of the types of and calculation of the extents
of hazardous areas which may be formed around gas installations covered by the High-pressure
Gas Safety Control Act (hereinafter referred to as “the High-pressure Gas Act”), the Safety Control
and Business of Liquefied Petroleum Gas Act (hereinafter referred to as “the Liquefied Gas Act”)
and the Urban Gas Business Act (hereinafter referred to as “the Urban Gas Act”).
1 General..........................................................................................................................................................................................1
1.1 Scope.................................................................................................................................................................................1
1.2 Validity of Code............................................................................................................................................................1
1.3 Refernce Codess and Standards...........................................................................................................................1
1.4 Definitions.......................................................................................................................................................................2
1.5 Application of Other Codes (currently not used).........................................................................................4
1.6 Interim Measures.........................................................................................................................................................4
2. Principle of Prevention of Explosive Hazards.............................................................................................................5
3. Classification of Hazardous Area Types........................................................................................................................6
3.1 General .............................................................................................................................................................................6
3.2 Determination of Grades of Release ..................................................................................................................6
3.2.1 Basic standard for classification of grades of release ..................................................................6
3.2.2 Special standard for classification of grades of release..............................................................7
3.3 Determination of Sizes of Release Holes.........................................................................................................9
3.3.1 Basic standard for determination of sizes of release holes.......................................................9
3.3.2 Special standard for determination of sizes of release holes .............................................11
3.4 Determination of Release Rates ........................................................................................................................12
3.4.1 Basic standard for determination of release rates......................................................................12
3.4.2 Special standard for determination of release rates..................................................................15
3.5 Determination of Dilution Grades....................................................................................................................16
3.5.1 Basic standard for classification of dilution grades....................................................................16
3.5.2 Special standard for classification of dilution grades ...............................................................20
3.6 Determination of Effectiveness of Ventilation.............................................................................................23
3.6.1 Basic standard for classification of effectiveness of ventilation ...........................................24
3.6.2 Special standard for classification of effectiveness of ventilation .......................................24
3.7 Determination of Areas.........................................................................................................................................25
3.7.1 Basic standard for classification of areas ...............................
