Okay, let's break down this situation with the electrical and data rooms and the mechanical exhaust duct, focusing on code compliance and best practices.

Electrical Room Considerations (NEC) NEC 110.26 - Spaces About Electrical Equipment

This is your primary concern.

(A) Working Space

You need adequate working space in front of electrical equipment operating at 600 volts or less. This involves depth, width, and height. Since you are calling for 6', you're most likely good here as you aren't working on high voltage equipment.

(E) Dedicated Equipment Space

This is the key area.

(1) Indoor

You're indoor. The code states, "In indoor electrical equipment rooms or areas, the space equal to the width and depth of the equipment and extending from the floor to a height of 6 ft (1.83 m) above the equipment or to the structural ceiling, whichever is lower, shall be dedicated to the electrical installation. No piping, ducts, or other equipment foreign to the electrical installation described in this section shall be located in this zone."

(2) Foreign Equipment

"Piping, ducts, leak protection apparatus, or other equipment foreign to the electrical installation shall not be installed in, enter, or pass through such spaces or rooms."

Interpretation

The NEC very clearly prohibits foreign piping and ductwork within the dedicated equipment space. You are proposing the exhaust duct to be above 12' AFF which may be more than 6' above the equipment but you need to define the height of the electrical equipment in the room. In a commercial building, there is usually a dropped ceiling, which means that your structural ceiling is much higher than your ceiling. You will need to take this into account.

Drip Pans

While you may think drip pans aren't needed because it's exhaust, any overhead piping or ductwork poses a potential hazard to electrical equipment. Consider condensation, leaks, or even accidental damage to the ductwork. Drip pans, while not explicitly required by the NEC in this situation, are highly recommended as a risk mitigation measure.

Accessibility

Ensure the ductwork doesn't impede access to electrical panels, disconnects, or other equipment for maintenance and repair.

Data Room Considerations (Beyond NEC)

The NEC has very little information regarding a "Data Room", therefore, you need to consider any applicable codes, standards, and best practices that govern data centers and server rooms. Consider the following. TIA-942 Telecommunications Infrastructure Standard for Data Centers

This is a widely recognized standard that provides guidelines for data center design and infrastructure. While not a legally binding code, it's considered a best practice and often used as a benchmark.

Environmental Control

TIA-942 emphasizes maintaining a stable and controlled environment for IT equipment, which includes temperature and humidity. Exhaust ducts running through the data room could impact the room's climate control, especially if they are not well-insulated.

Physical Security

Consider the security implications. Is the ductwork easily accessible? Could it be used to gain unauthorized access to the data room?

Manufacturer Specifications

IT equipment (servers, network gear) has specific environmental requirements. Check the manufacturer's specifications for temperature, humidity, and air quality. The exhaust duct could affect these parameters.

Airflow and Contamination

Data rooms are sensitive to dust and other contaminants. Exhaust ducts, especially if not properly sealed, could introduce contaminants into the data room.

Condensation

As with the electrical room, condensation on the ductwork is a major concern. Condensation can drip onto sensitive IT equipment, causing damage and downtime.

Maintenance Access

Ensure the ductwork does not obstruct access to IT equipment for maintenance, upgrades, or repairs.

Fire Suppression

Consider the impact on the fire suppression system. Will the ductwork interfere with the sprinklers or other fire suppression measures?

Code Implications of Obstruction The issue is that by the strictest interpretation of NEC 110.26(E), any foreign equipment passing through the electrical room is a violation. Even if it's above 6 feet. The code is designed to keep that space clear and dedicated. While not strictly NEC, any obstruction in the data room can create its own problems. The primary concern is maintaining a stable, clean, and safe environment for sensitive IT equipment.

Possible Solutions and Mitigation1. Reroute the Ductwork (Best Option)

Seriously explore every possible alternative route for the exhaust duct. This is the preferred solution. Can it go around the rooms, through a different corridor, or outside the building?2.

Enclose the Ductwork

If rerouting is truly impossible, consider fully enclosing the ductwork within a fire-rated and sealed enclosure. This enclosure should: Be structurally independent of the electrical and data room structures. Provide its own support system. Be properly insulated to prevent condensation. Have its own access panels for maintenance outside the electrical and data rooms. This enclosure might be considered separate enough to satisfy the NEC, but it would require a very careful interpretation by the AHJ.3.

Drip Pans and Monitoring

If enclosure is not possible, install large drip pans under the entire length of the ductwork in both rooms. Install moisture sensors and alarms to detect any leaks or condensation.4.

Airflow Management

In the data room, implement airflow management strategies to ensure that the exhaust duct does not negatively impact the cooling of IT equipment. This may involve hot aisle/cold aisle containment, blanking panels, and other techniques.5.

Seismic Bracing

Ensure the ductwork is properly seismically braced to prevent damage or collapse during an earthquake (if applicable in your area).6.

Consult with the AHJ

Before proceeding with any solution, discuss the situation with the Authority Having Jurisdiction (AHJ). They will have the final say on whether the proposed solution meets code requirements.7.

Documentation

Document everything. Keep records of the code interpretations, AHJ approvals, engineering calculations, and any modifications made to the electrical and data room systems.

In Summary Electrical Room

The NEC is quite strict about dedicated equipment space. You need to avoid ductwork passing through the electrical room's dedicated space. If it is unavoidable, you will need to find a way to work around the code with an enclosure.

Data Room

Focus on maintaining a stable, clean, and safe environment for IT equipment. Minimize the impact of the exhaust duct on temperature, humidity, airflow, and contamination.

Communication: Communicate effectively with all stakeholders (architects, engineers, contractors, building owners) to find the best solution.This is a complex situation, and it's essential to prioritize safety and compliance. Seek expert advice from qualified electrical and mechanical engineers to ensure that your solution meets all applicable codes and standards. Flag for review