Cross Reference Table for Area Classification Details
Equipment
Area Focus
Cross Reference for Area Classification
Specific
Details Per Recommended Practices
Equipment/Scenario
API RP 500
NFPA 497
NFPA 499
Adjacent Areas
Adequately ventilated nonenclosed
area adjacent to a classified area
Enclosed area with vaportight barriers
adjacent to a classified area
Enclosed area with non-vaportight
barriers adjacent to a classified area
and in contact with its Division 1
hazardous influence boundary
Enclosed area with non-vaportight
barriers adjacent to a classified area
and in contact with its Division 2
hazardous influence boundary
Figure 2
Figure 3
Figure 4
Figure 5
Bulk Loading or Unloading
Drum Filling Station
(Outdoors or Indoors in
an Adequately
Ventilated Building))
Marine Terminal
Tank Car or Tank Truck
Loading and Unloading
Via Closed System
Tank Car or Tank Truck
Loading and Unloading
Via Open System
Handling Flammable Liquid
Figure 5.9.6
Handling Flammable or Combustible
Liquid
Product Transfer through Bottom
Only for Flammable Liquid
Figure 19
Figure 5.9.14
Figure 11
Product Transfer through Dome Only
for Flammable Liquid
Figure 10
 Tank Truck:
Figure
5.9.4(d)
 Tank Car:
Figure
5.9.4(c)
Tank Car
Only: Figure
5.9.4(b)
Product Transfer through Bottom
Only for Liquefied Gas, Compressed
Gas, or Cryogenic Liquid
Product Transfer through Dome Only
for Flammable Liquefied Gas,
Compressed Gas, or Cryogenic Liquid
Product Transfer through Top or
Bottom for Flammable Liquid
Figure 13
Figure 9
Figure 5.9.5
Figure 12
Figure 5.9.4(e)
Compressors
Compressor Below
Grade
(Inadequately Ventilated
Area)
Compressor at Grade
(Outdoors)
Handling Flammable or Combustible
Gas or Vapor or Highly Volatile
Liquids (HVL)
Figure 101
Handling Flammable or Combustible
Gas or Vapor
Handling Highly Volatile Liquid
(HVL)
Figure 51
Page 1 of 10
Figure 93
Figure 5.9.2(a)
Cross Reference Table for Area Classification Details (cont.)
Equipment
Compressor
(Inside Adequately
Ventilated Compressor
Shelter)
Compressor
(Inside Inadequately
Ventilated Compressor
Shelter)
Compressor
(Outdoors but Under
Roofed Building without
Sides)
Compressor
(Inside Adequately
Ventilated Roofed
Building with One or
More Sides)
Compressor
(Inside Inadequately
Ventilated Roofed
Building with One or
More Sides)
Compressor
(Indoor with Enclosed
Operating Equipment)
Compressor
(Indoor with Open or
Semi-Enclosed
Operating Equipment)
Compressor
(Indoor, Walled Off
Area, Enclosed
Operating Equipment)
Cross Reference for Area Classification
Specific
Details Per Recommended Practices
Equipment/Scenario
API RP 500
NFPA 497
NFPA 499
Compressors (cont.)
Handling Lighter-Than-Air
Flammable or Combustible Gas or
Vapor
Figure 23
Figure 5.9.9(a)
Handling Lighter-Than-Air
Flammable or Combustible Gas or
Vapor
Figure 25
Figure 5.9.9(b)
Handling Flammable or Combustible
Gas or Vapor
Handling Highly Volatile Liquid
(HVL)
Handling Lighter-Than-Air
Flammable or Combustible Gas or
Vapor
Handling Flammable or Combustible
Gas or Vapor
Handling Flammable or Combustible
Liquid or Highly Volatile Liquid
(HVL)
Handling Lighter-Than-Air
Flammable or Combustible Gas or
Vapor
Handling Flammable or Combustible
Gas or Vapor
Handling Flammable or Combustible
Liquid or Highly Volatile Liquid
(HVL)
Groups F or G Dust with no visible
dust cloud, dust layer less than 1/8
inch and surface color not discernable
Groups F or G Dust with no visible
dust cloud or dust layer and surface
color discernable
Group E Dust with moderate or dense
dust cloud, dust layer greater than 1/8
inch to less than 1/8 inch and surface
color not discernable
Groups F or G Dust with moderate or
dense dust cloud to no visible dust
cloud, dust layer greater than 1/8 inch
to less than 1/8 inch and surface color
not discernable
Group E Dust
Figure 52
Page 2 of 10
Figure 52 with
Figure 93
Figure 105
Figure 53
Figure 94
Figure 106
Figure 54
Figure 95
Figure 5.8(c)
Figure 5.8(d)
Figure 5.8(b)
Figure 5.8(a)
Figure 5.8(f)
Cross Reference Table for Area Classification Details (cont.)
Equipment
Drain System
(Enclosed Area)
Drain System
(Enclosed Area)
(cont.)
Drain System
(Nonenclosed Area)
Emergency
(Above Grade)
Emergency or
Temporary
(Below Grade)
Sump
(Adequately Ventilated
Enclosed Area)
Sump
(Inadequately Ventilated
Enclosed Area)
Sump
(Nonenclosed
Adequately Ventilated
Area)
Cross Reference for Area Classification
Specific
Details Per Recommended Practices
Equipment/Scenario
API RP 500
NFPA 497
NFPA 499
Effluent Handling and Treatment
Type 1 Open Drain System
Figure 58
Type 2 Open Drain System
Adequately ventilated Type 3 Open
Drain System
Type 4 Open Drain System
Inside Adequately Ventilated Building
handling Cryogenic Flammable
Liquids including Natural Gas
Type 1 Open Drain System
Type 2 Open Drain System
Adequately ventilated Type 3 Open
Drain System
Adequately ventilated Type 4 Open
Drain System
Handling Cryogenic Flammable
Liquids including Natural Gas
 Impounding Basin
 Oil-Water Separator
handling Flammable Liquid
 Drainage Ditch
 Oil-Water Separator
handling Flammable Liquid
Below grade Open Sump handling
Flammable or Combustible Liquid
Figure 59
Figure 61
Above Grade Sump inside an
enclosure handling Flammable or
Combustible Liquid
Below Grade Open Sump Inside Open
Vault or Containment Area
Below grade Open Sump handling
Clean Water
Below grade Open Sump handling
Flammable or Combustible Liquid
Below grade Closed Sump or Oily
Water Separator with Atmospheric
Vent and No Access Hatch(es)
Below grade Closed Sump or Oily
Water Separator with Vent to Carbon
Cannisters and No Access Hatch(es)
Page 3 of 10
Figure 63
Figure 5.9.13,
Top Detail
Figure 58
Figure 59
Figure 60
Figure 62
Figure 5.9.13,
Bottom Detail
Figure 5.9.7,
Top Detail
Figure 5.9.7,
Bottom Detail
Figure 57 with
Division 2 for the
remainder of the
enclosed area
Figure 34
Figure 63
Figure 58
Figure 57
Figure 27 –
Detail 4
1. Figure 27 Detail 4 but
without Vent
classification
2. Add Vent note
“To Carbon
Cannisters”
Cross Reference Table for Area Classification Details (cont.)
Equipment
Cross Reference for Area Classification
Specific
Details Per Recommended Practices
Equipment/Scenario
API RP 500
NFPA 497
NFPA 499
Effluent Handling and Treatment (cont.)
Sump
(Nonenclosed
Adequately Ventilated
Area)
(cont.)
Below grade Closed Sump or Oily
Water Separator with Atmospheric
Vent and Access Hatch(es)
Waste Water Treatment
(Nonenclosed
Adequately Ventilated
Area)
Open Top Below Grade Separator or
Preseparator
Open Top Above Grade Separator or
Preseparator
Fixed Roof Above Grade Separator or
Preseparator
Open Top Below Grade Dissolved Air
Flotation (DAF) Unit
Open Top Above Grade Dissolved Air
Flotation (DAF) Unit
Fixed Roof Above Grade Dissolved
Air Flotation (DAF) Unit
Open Top Below Grade Biological
Oxidation (BIOX) Unit
Open Top Above Grade Biological
Oxidation (BIOX) Unit
Fixed Roof Above Grade Biological
Oxidation (BIOX) Unit
Injecton Well without Cellar or Below
Grade Sump
Injecton Well with Inadequately
Ventilated Cellar or Below Grade
Sump
Below grade Closed Sump or Oily
Water Separator with Vent to Carbon
Cannisters and Access Hatch(es)
1. Figure 27 –
Detail 4
2. Figure 100 –
Detail B
1. Figure 27 –
Detail 4 but
without Vent
classification
2. Add Vent note
“To Carbon
Cannisters”
3. Figure 100 –
Detail B
Figure 27 –
Detail 1
Figure 7
Figure 6
Figure 27 –
Detail 2
Figure 7
Figure 6
Figure 27 –
Detail 3
Figure 7
Figure 6
Figure 39
Figure 40
General Process Equipment
Above Grade Source
with Closure
(Nonenclosed
Adequately Ventilated
Area)
Cooling Tower
Diverter Line Outlet handling
Flammable or Combustible Liquid
Pig Launching or Receiving
Installation handling Flammable or
Combustible Liquid
Process Filter or Strainer handling
Flammable or Combustible Liquid or
Highly Volatile Liquid (HVL)
Mechanical Draft handling Process
Cooling Water
Page 4 of 10
Figure 89
Figure 49
Figure 102
Figure 28
Cross Reference Table for Area Classification Details (cont.)
Equipment
Dust Handling
Equipment
(Indoor with Enclosed
Operating Equipment)
Dust Handling
Equipment
(Indoor with Open or
Semi-Enclosed
Operating Equipment)
Dust Handling
Equipment
(Indoor, Walled Off
Area, Enclosed
Operating Equipment)
Fired Equipment
Cross Reference for Area Classification
Specific
Details Per Recommended Practices
Equipment/Scenario
API RP 500
NFPA 497
NFPA 499
General Process Equipment (cont.)
Groups F or G Dust with no visible
dust cloud, dust layer less than 1/8
inch and surface color not discernable
Groups F or G Dust with no visible
dust cloud or dust layer and surface
color discernable
Group E Dust with moderate or dense
dust cloud, dust layer greater than 1/8
inch to less than 1/8 inch and surface
color not discernable
Groups F or G Dust with moderate or
dense dust cloud to no visible dust
cloud, dust layer greater than 1/8 inch
to less than 1/8 inch and surface color
not discernable
Group E Dust
Fired Heater with air-aspirated burners
Fired Heater with FD fan or FD/ID
fans and safety shutdown system
Fired Heater with FD fan or FD/ID
fans and no safety shutdown system
Flare
Flammable GasBlanketed and Produced
Water-Handling
Equipment
Located Outdoors at Grade in a
Nonenclosed Adequately Ventilated
Area
Located at Grade in Adequately
Ventilated Enclosed Area and all
Vents extend outside enclosed area
Located at Grade in Adequately
Ventilated Enclosed Area and all
Vents do not extend outside enclosed
area
Located at Grade in an Inadequately
Ventilated Enclosed Area
Page 5 of 10
Figure 5.8(c)
Figure 5.8(d)
Figure 5.8(b)
Figure 5.8(a)
Figure 5.8(f)
Unclassified
entending out 10
feet from perimeter
of burner bank
Unclassified
Figure 48
Unclassified
entending out 10
feet from tip
Figure 50
Figure 50 with
Division 2 for the
remainder of the
extent of enclosed
area
Figure 50 with the
remainder of the
extent of enclosed
area Division 1
Figure 50 with
Division 1 for the
extent of enclosed
area
Cross Reference Table for Area Classification Details (cont.)
Equipment
More than One Piping
System With Multiple
Valves, Screwed
Fittings, Flanges, Hoses,
etc. in Close Proximity:
 Metering Skid
 Manifolds
 Prover Skid
 Sampler System
 Chemical Injection
Skid
Plate and Frame Filter
Press
(Adequate Ventilation)
Product Dryer
(Inside Adequately
Ventilated Butilding)
Cross Reference for Area Classification
Specific
Details Per Recommended Practices
Equipment/Scenario
API RP 500
NFPA 497
NFPA 499
General Process Equipment (cont.)
Located Outdoors at Grade handling
Flammable or Combustible Liquid or
Highly Volatile Liquid (HVL)
Located Outdoors at Grade handling
Cold Liquefied Flammable Gas
including Liquefied Natural Gas
Located in Inadequately Ventilated
Process Location handling HeavierThan-Air Flammable or Combustible
Gas or Vapor or Highly Volatile
Liquid (HVL)
Located in Inadequately Ventilated
Process Location handling LighterThan-Air Flammable or Combustible
Gas or Vapor
Located Inside Adequately Ventilated
Roofed Building with One or More
Sides handling Flammable or
Combustible Liquid or Highly Volatile
Liquid (HVL)
Located Inside Adequately Ventilated
Roofed Building with One or More
Sides handling Cold Liquefied
Flammable Gas including Liquefied
Natural Gas
Located Inside Inadequately
Ventilated Roofed Building with One
or More Sides handling Flammable or
Combustible Liquid or Highly Volatile
Liquid (HVL)
Handling a Solid wet with a
Flammable Liquid
Handling a Solid wet with a
Flammable Liquid
Figure 96
Figure 5.9.1(g)
Figure 5.9.11
Figure 22
Figure 26
Figure 97
Figure 5.9.13
Figure 5.9.12
Figure 98
Figure 5.9.3(b)
Figure 5.9.3(a)
Hydrocarbon Pressure Vessels
(e.g. Heat Exchanger (Hazardous Material Shell-side),
Fin-Fan Heat Exchanger, Reactor, Accumulator, Oil-gas Separator, Tower)
Multiple Sources of
Leakage from Process
Equipment Located on
More than One Floor
In Adequately Ventilated Building
Handling a Flammable Liquid
In Outdoor Process Area Handling a
Flammable Liquid
Page 6 of 10
Figure 5.9.1(n)
Figure 5.9.1(k)
or
Figure 5.9.1(l)
or
Figure
5.9.1(m)
Cross Reference Table for Area Classification Details (cont.)
Cross Reference for Area Classification
Specific
Details Per Recommended Practices
Equipment/Scenario
API RP 500
NFPA 497
NFPA 499
Hydrocarbon Pressure Vessels (cont.)
(e.g. Heat Exchanger (Hazardous Material Shell-side),
Fin-Fan Heat Exchanger, Reactor, Accumulator, Oil-gas Separator, Tower)
Equipment
Vessel
(Inside Inadequately
Ventilated Process
Enclosure)
Vessel
(Inside Adequately
Ventilated Roofed
Building with One or
More Sides)
Vessel
(Inside Inadequately
Ventilated Roofed
Building with One or
More Sides)
Vessel
(Indoor with Enclosed
Operating Equipment)
Vessel
(Indoor with Open or
Semi-Enclosed
Operating Equipment)
Vessel
(Indoor, Walled Off
Area, Enclosed
Operating Equipment)
Handling Heavier-Than-Air
Flammable or Combustible Gas or
Vapor or Highly Volatile Liquid
(HVL)
Handling Lighter-Than-Air
Flammable or Combustible Gas or
Vapor
Handling Lighter-Than-Air
Flammable or Combustible Gas or
Vapor
Handling Flammable or Combustible
Liquid or Highly Volatile Liquid
(HVL)
Source above Floor Level handling
Flammable or Combustible Liquid or
Highly Volatile Liquid (HVL)
Handling Cold Liquefied Gas
including Liquefied Natural Gas
Handling Lighter-Than-Air
Flammable or Combustible Gas or
Vapor
Handling Flammable or Combustible
Liquid or Highly Volatile Liquid
(HVL)
Groups F or G Dust with no visible
dust cloud, dust layer less than 1/8
inch and surface color not discernable
Groups F or G Dust with no visible
dust cloud or dust layer and surface
color discernable
Group E Dust with moderate or dense
dust cloud, dust layer greater than 1/8
inch to less than 1/8 inch and surface
color not discernable
Groups F or G Dust with moderate or
dense dust cloud to no visible dust
cloud, dust layer greater than 1/8 inch
to less than 1/8 inch and surface color
not discernable
Group E Dust
Page 7 of 10
Figure 22
Figure 26
Figure 105
Figure 97
Figure 5.9.1(j)
Figure 5.9.1(d)
Figure 5.9.12
Figure 106
Figure 98
Figure 5.9.1(i)
Figure 5.8(c)
Figure 5.8(d)
Figure 5.8(b)
Figure 5.8(a)
Figure 5.8(f)
Cross Reference Table for Area Classification Details (cont.)
Cross Reference for Area Classification
Specific
Details Per Recommended Practices
Equipment/Scenario
API RP 500
NFPA 497
NFPA 499
Hydrocarbon Pressure Vessels (cont.)
(e.g. Heat Exchanger (Hazardous Material Shell-side),
Fin-Fan Heat Exchanger, Reactor, Accumulator, Oil-gas Separator, Tower)
Equipment
Vessel Below Grade
(Inadequately Ventilated
Area)
Vessel at Grade
(Nonenclosed
Adequately Ventilated
Area)
Vessel Above Grade
(Nonenclosed
Adequately Ventilated
Area)
Handling Flammable or Combustible
Liquid or Highly Volatile Liquid
(HVL)
Handling Flammable or Combustible
Liquid
Handling Cold Liquefied Flammable
Gas including Liquefied Natural Gas
Handling Flammable or Combustible
Liquid
Figure 101
Handling Highly Volatile Liquid
(HVL)
Figure 21 with
Figure 99
Figure 48
Figure 5.9.11
Figure 99
Handling Cold Liquefied Flammable
Gas including Liquefied Natural Gas
Handling Liquified or Compressed
Flammable Gas or Cryogenic
Flammable Liquid
When Flammable Gas is vented to the
inside of enclosure (control panel)
Figure 64
Adequately ventilated control panel
(enclosure) with instruments inside
Inadequately ventilated control panel
(enclosure) with instruments inside
Located in nonenclosed adequately
ventilated area
Figure 66
Adequately ventilated area
Inadequately ventilated area
Figure 63
Located in enclosed inadequately
ventilated area
Sample Valve
(Discharge located in
Enclosed Area)
Figure 65
Division 2 extends
18 inches from
stem seal (not
shown on plot plan
or support
drawing)
Division 2 to the
extent of the
enclosed area
Division 1 to the
extent of the
enclosed area
Figure 61
Located in enclosed adequately
ventilated area
Page 8 of 10
Figure 5.9.1(b)
or
Figure 5.9.1(h)
or
Figure 5.9.2(b)
Figure 5.9.1(b)
or
Figure 5.9.1(h)
Figure 5.9.11
Figure 5.9.2(b)
Instrumentation
Control Panel
(Enclosure) for
Instruments having
Connections to
Flammable or
Combustible Fluids
(Instruments located
Inside or Attached to
Panel)
Process Control Valve
Figure 5.9.1(g)
Cross Reference Table for Area Classification Details (cont.)
Equipment
Pump Below Grade but
External to Associated
Equipment
(Inadequately Ventilated
Area)
Pump at Grade
(Outdoors)
Pump
(Outdoors but Under
Roofed Building without
Sides)
Pump
(Inside Adequately
Ventilated Roofed
Building with One or
More Sides)
Pump
(Inside Inadequately
Ventilated Roofed
Building with One or
More Sides)
Specific
Equipment/Scenario
Pumps
Pump associated with Oil-gas
Separator, Receiver, Sump, etc.
handling Flammable or Combustible
Liquid or Highly Volatile Liquid
(HVL)
Handling Flammable or Combustible
Liquid
Handling Highly Volatile Liquid
(HVL)
Handling Liquefied or Compressed
Flammable Gas or Flammable
Cryogenic Liquid
Handling Flammable or Combustible
Liquid
Handling Highly Volatile Liquid
(HVL)
Handling Flammable or Combustible
Liquid
Handling Flammable or Combustible
Liquid or Highly Volatile Liquid
(HVL)
Handling Flammable or Combustible
Liquid
Handling Flammable or Combustible
Liquid or Highly Volatile Liquid
(HVL)
Cross Reference for Area Classification
Details Per Recommended Practices
API RP 500
NFPA 497
NFPA 499
Figure 101
Figure 51
Figure 5.9.2(a)
Figure 93
Figure 5.9.1(a)
Figure 5.9.2(a)
Figure 52
Figure 52 with
Figure 93
Figure 53
Figure 94
Figure 5.9.1(c)
or
Figure 5.9.1(e)
Figure 54
Figure 95
Figure 5.9.1(f)
Storage
Storage Area
Storage Tank
(Nonenclosed
Adequately Ventilated
Area)
Storage Tank for
Cryogenic and other
Cold Liquefied
Flammable Gases
(Outdoors)
 Bags
 Drums
 Closed Hoppers
handling Groups E, F, or G Dusts
Fixed Roof Flammable Liquid Storage
Tank
Fixed Roof Flammable Liquid Storage
Tank with Internal Floating Roof
Open Top Floating Roof Flammable
Liquid Storage Tank
Fixed Roof Combustible Liquid
Storage Tank
Dike height less than distance from
container to dike
Dike height greater than distance from
container to dike
Conainer with liquid level below
grade or top of dike
Page 9 of 10
Figure 5.8(e)
Figure 6
Figure 5.9.4(a)
Figure 6
Figure 7
Figure 8
Figure
5.9.10(a)
Figure
5.9.10(b)
Figure
5.9.10(c)
Cross Reference Table for Area Classification Details (cont.)
Equipment
Cross Reference for Area Classification
Specific
Details Per Recommended Practices
Equipment/Scenario
API RP 500
NFPA 497
NFPA 499
Storage (cont.)
Storage for Hydrogen
(Indoors in an
Adequately Ventilated
Building)
Storage for Hydrogen
(Outdoors)
Gaseous Hydrogen only
Figure 5.9.8(b)
Liquid Hydrogen only
Figure 5.9.8(a)
Gaseous Hydrogen only
Liquid Hydrogen only
Figure 5.9.8(b)
Figure 5.9.8(a)
Vent To Atmosphere
(Nonenclosed
Adequately Ventilated)
From a Division 1 Area
Vents
Vent To Atmosphere
(Indoors Adequately
Ventilated Building)
From a Division 2 Area
From Instrument or Control Device
(Low Pressure)
From Process Equipment
From Relief Valve
From Rupture Disk
From source handling Cryogenic
Flammable Liquids including Natural
Gas
From source handling Cryogenic
Flammable Liquids including Natural
Gas
Figure 16 or
Figure 87
Figure 17 or
Figure 88
Figure 15
Figure 14
Figure 18
Figure 18
Figure 5.9.13,
Bottom Detail
Figure 5.9.13,
Top Detail
Notes:
1. NFPA Figures above use “Division” nomenclature. The use of NFPA Figures with “Zone” nomenclature is
discouraged.
2. See Section 5.10 for Highly Volatile Liquid (HVL), Flammable Liquid, and Combustible Liquid definitions.
3. Specific radius dimensions for use with the Figures above should be obtained from Gas/Vapor Dispersion
modeling results.
4. If modeling results cannot be obtained (e.g. composition of material is unknown), use the recommended radius
per the specific figure.
Page 10 of 10