What are the G1, G2, G3 and Gx classifications for the ANSI Standard, ANSI/ISA S71.04-1985, “Environmental Conditions for Process Measurement and Control Systems: Airborne Contaminants,”?

The G3 specification references the ANSI Standard, ANSI/ISA S71.04-1985, “Environmental Conditions for Process Measurement and Control Systems: Airborne Contaminants,” .

The G reference refers to the severity and classification of the test and it can be G1 (Mild, Moderate, Harsh and Severe (G1, G2, G3 and Gx, respectively).  The classification directly correlates with the level of corrosive effects in that environment and the standards define or characterise environments in terms of their overall corrosion potential.

G1 Mild <300Å
An environment sufficiently well-controlled such that corrosion is not a factor in determining equipment reliability.

G2 Moderate <1000 Å
An environment in which the effects of corrosion are measurable and corrosion may be a factor in determining equipment reliability.

G3 Harsh <2000 Å
An environment is which there is a high probability that corrosive attack will occur. These harsh levels should prompt further evaluation resulting in environmental controls or specially design and packaged equipment.

GX Severe >2000 Å
An environment in which only specially designed and packaged equipment would be expected to survive. Specifications for equipment in this class are a matter of negotiation between user and supplier.

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