You're right to question this, as the interpretation seems inconsistent. Here's a breakdown of NFPA 79 11.2.
2.2 and why your I/O may have been allowed to stay

Understanding NFPA 79 11.2.
2.2

The core of this section is about segregation of fluids and electrical components. The goal is to prevent flammable, corrosive, or conductive fluids from damaging or interfering with electrical components, potentially causing: Electrical shock hazards

Fluids can conduct electricity, creating shock risks.

Fire hazards

Flammable fluids near electrical arcs or heat sources are dangerous.

Corrosion and damage

Fluids can corrode or damage electrical components, leading to failures.

Reduced reliability

Fluid contamination can cause malfunctions.

Why the Pump Controllers Had to Go

Based on the information you've provided, the 2kW 208VAC pump controllers almost certainly had to be moved for these reasons: Voltage Level

They operate at 208VAC, a significant voltage that poses a greater shock and fire hazard if exposed to fluids.

Power Level

2kW is a substantial power level, meaning a fault could result in a significant electrical arc and a higher risk of ignition if flammable fluids are present.

Possible Explanations for Keeping the I/O

Here are the most likely reasons why the I/O was allowed to stay, despite the general prohibition in NFPA 79 11.2.
2.2:1. Low Voltage and Limited Energy

The most probable explanation is the low voltage (24VDC) and limited energy of the I/O cards. A 24VDC circuit, especially one with limited current, poses a much lower shock and fire hazard compared to a 208VAC, 2kW pump controller. NFPA 79 aims to mitigate significant electrical hazards related to fluid exposure. Small control signals at low voltage are generally considered less risky.2.

Enclosure Rating and Fluid Containment

The inspector may have considered the

enclosure rating and the likelihood of fluid leaks. If the enclosure was rated to protect against fluid ingress (e.g., NEMA 4/IP66), and the piping and valves were installed with a very low risk of leaks (e.g., using robust fittings and materials compatible with the fluids), the risk might have been deemed acceptable for the low-voltage I/O.3. Risk Assessment and Mitigation

The inspector might have performed a risk assessment that considered the specific installation, the types of fluids, the likelihood of leaks, and the potential consequences. If the risk was deemed low, even with the I/O present, it could have been acceptable. However, this would typically require documentation of the risk assessment.4.

Alternative Interpretation (Less Likely)

It's possible (but less likely) that the inspector interpreted the rule very strictly to only exclude devices handling the fluids themselves. The I/O, while being electrical, isn't directly involved in the handling of air, gases, or liquids. This is a weaker argument, but depending on the inspector's approach, it could have been a factor.

Important Considerations Authority Having Jurisdiction (AHJ)

The ultimate interpretation of NFPA 79 lies with the AHJ (the inspection authority). It's possible the inspector had a specific reason or local interpretation that influenced the decision.

Documentation

The lack of documentation is a significant problem. You need a clear record of the safety audit findings and rationale.

Current NFPA 79 Edition

Ensure you're working with the latest edition of NFPA 79. Standards are updated regularly, and requirements may have changed.

Machine-Specific Risk Assessment

Even if the I/O was deemed acceptable in the past, a new risk assessment is advisable, especially if the machine has been modified or if you have any doubts about the safety of the current configuration.

Local Codes and Regulations

Be aware of any local electrical codes or regulations that might supplement or supersede NFPA 79.

Recommendations1. Consult a Qualified Electrical Safety Professional

The best course of action is to consult a qualified electrical safety professional with expertise in NFPA 79 and industrial machinery. They can perform a new risk assessment and provide guidance on compliance.2.

Review the Installation

Carefully examine the installation of the I/O, piping, and valves. Look for any signs of potential leaks or damage.3.

Document Everything

Meticulously document all safety-related decisions, risk assessments, and justifications.4.

Consider Separation Even for Low Voltage: Even if the I/O is technically compliant, consider whether you can reasonably relocate it to a separate compartment to improve safety and reduce the risk of fluid contamination.In summary, while NFPA 79 generally prohibits mixing fluids and electrical equipment, the low voltage and limited energy of the I/O likely played a significant role in the inspector's decision to allow it to remain in the compartment. However, without proper documentation, it's impossible to know the exact rationale. Consulting a qualified safety professional is strongly recommended to ensure compliance and safety. Flag for review