Case Study: Smoke Detector System Layout for Gym & Dance Studio in Clark, NJ

Voluntary NFPA 72 Smoke Detection Design for an A-3 Assembly Space

NextBLDG Architecture & Engineering, P.C. developed a comprehensive smoke detector system layout for a proposed hot yoga studio, gym, and dance facility located in Clark, New Jersey. The occupancy classification for the space is Group A-3 Assembly.

Under the 2021 New Jersey Uniform Construction Code, a fire alarm system is not required for this specific project due to occupant load and building configuration. However, the owners elected to install a voluntary smoke detection system designed in accordance with NFPA 72 to enhance life safety and property protection.

This case study outlines the code analysis, system selection, detector placement strategy, and engineering rationale behind the final layout.

At NextBLDG, we integrate code analysis, life safety planning, and practical architectural coordination to produce systems that are compliant, buildable, and defensible during Authority Having Jurisdiction review. For structural engineering services in Union, NJ, architecture in Syracuse, building system design, or something else, give us a call.

Code Analysis and Regulatory Basis

Before designing any fire alarm or detection system, we first evaluate whether it is required by code.

Applicable Codes

The project was reviewed under:

• NFPA 72 National Fire Alarm and Signaling Code
• 2021 New Jersey Uniform Construction Code
• 2021 New Jersey Building Code

Further reading: https://www.nfpa.org/codes-and-standards/all-codes-and-standards/detail?code=72

Further reading: https://www.nj.gov/dca/divisions/codes/

A-3 Assembly Threshold Review

Under the New Jersey Building Code and IBC 2021, a manual fire alarm system is required for Group A occupancies when:

• The occupant load is 300 or greater, or
• More than 100 occupants are located above or below the level of exit discharge

For this project:

• Occupant load was calculated at 49
• The space is located above grade
• The building is non-sprinklered

Based on these conditions, a fire alarm system is not mandated.

Engineering Conclusion

Although not required, voluntary smoke detection was recommended to:

• Provide early warning detection
• Improve life safety for occupants
• Enhance property protection
• Support insurance and risk management objectives

Voluntary Fire Alarm System Design Approach

When designing a voluntary system, it is essential to maintain compliance with NFPA 72 so the installation meets professional standards and avoids confusion during plan review.

System Configuration

The proposed system includes:

• An addressable fire alarm control unit
• Ceiling-mounted smoke detectors in key areas
• Optional manual pull stations at primary exits
• Notification appliances as appropriate

Documentation Strategy

To prevent misinterpretation by plan reviewers, construction drawings should clearly indicate that the system is voluntary and not triggered by Section 907.2.1 requirements.

The fire alarm narrative should include:

• Building use and A-3 occupancy classification
• Confirmed occupant load of 49
• Non-sprinklered condition
• Confirmation that no high-rise or smoke control triggers apply
• Engineering rationale for detector placement

Clear documentation ensures smooth AHJ review and avoids unnecessary compliance upgrades.

NFPA 72 Smoke Detector Placement Principles

NFPA 72 provides general spacing guidelines for smooth ceilings.

For standard ceiling conditions:

• Nominal spacing is 30 feet
• Each detector covers approximately 900 square feet
• No point on the ceiling should exceed prescribed distance limits

Spacing must be adjusted based on:

• Ceiling height
• HVAC airflow patterns
• Obstructions
• Beams or soffits

Installation requirements include:

• Placement at least 4 inches from walls
• Avoidance of HVAC diffusers and return air grilles
• Accessibility for maintenance

The subject building uses a 10-foot drop ceiling, which simplifies layout and supports standard spot-type detector installation.

Room-by-Room Smoke Detector Layout

Studio Room – 948 Square Feet

Although not required by code, two ceiling-mounted smoke detectors were recommended.

Placement strategy included:

• Locating detectors along the centerline
• Spacing approximately 18 to 20 feet apart
• Ensuring no point on the floor exceeds recommended coverage radius
• Avoiding ball-impact zones or specifying protective cages

This layout aligns with typical NFPA 72 spacing assumptions for a 10-foot ceiling.

Foyer and Primary Entrance

One centrally located smoke detector was recommended in the foyer area.

Placement considerations included:

• Positioning between main entry doors and corridor intersection
• Maintaining manufacturer-required clearances
• Avoiding HVAC interference

This ensures early detection in the primary circulation space.

Hallway to Locker Rooms and Restrooms

One smoke detector was centered within the main corridor segment.

Design considerations:

• Providing coverage for egress paths
• Avoiding installation within restroom spaces due to steam and aerosol interference
• Considering heat detection in areas subject to humidity

Locker Room

One centrally located smoke detector was recommended for the locker area.

Placement avoided:

• Direct proximity to supply diffusers
• Areas prone to steam or aerosol accumulation

Storage Room or Closet

A smoke detector was recommended where storage or small office functions introduce potential ignition sources.

Placement was centered on the ceiling for balanced coverage.

Ceiling Height and Installation Considerations

The 10-foot drop ceiling condition supports:

• Standard spot-type detector listings
• Flush mounting within ceiling tiles
• Simplified wiring coordination

Care was taken to:

• Avoid ceiling pockets or recessed areas
• Maintain service access
• Ensure device visibility during inspection

Benefits of Installing a Voluntary Detection System

While not mandated, voluntary smoke detection provides meaningful benefits.

These include:

• Early warning during unoccupied hours
• Enhanced life safety during classes and events
• Reduced potential property loss
• Increased confidence from insurers and authorities

Voluntary systems are common in fitness studios, dance facilities, martial arts centers, and other small assembly occupancies.

Project Outcome

The final smoke detector layout for the facility at 1120 Raritan Road provides a fully NFPA 72-compliant voluntary system without triggering additional regulatory requirements.

The design achieves:

• Alignment with NFPA 72 spacing principles
• Consistency with 2021 New Jersey code requirements
• Clear documentation for AHJ review
• Enhanced life safety for occupants

The system remains cost-effective, maintainable, and proportionate to the facility’s risk profile.

Why NextBLDG Designs Voluntary Life Safety Systems Strategically

Voluntary systems must be carefully designed. Overdesign can unintentionally trigger additional code requirements. Underdesign can create reliability issues or AHJ concerns.

NextBLDG evaluates:

• Occupancy classification
• Threshold triggers
• Life safety intent
• System scalability
• Architectural coordination

Because we provide both architectural and engineering services, detector placement is coordinated with ceiling layout, lighting, HVAC, and finish design from the outset.

Work With a Design Team That Integrates Code and Practical Application

Even when not required by code, life safety systems should be designed with the same rigor as mandated installations. Proper documentation, spacing calculations, and architectural coordination ensure systems function as intended and are accepted by reviewing officials.

If you are developing a gym, studio, small assembly space, or tenant fit-out and are considering voluntary smoke detection or fire alarm upgrades, NextBLDG Architecture & Engineering, P.C. can provide code analysis, compliant system layout, and coordinated construction documentation that aligns with your project’s scope and risk profile.