Start from the use and occupant load of each underground area, then check that the egress routes, smoke control, fire protection, emergency power, and communications on each discipline’s drawings serve the same areas. AI can flag conflicts; the design team and the authority having jurisdiction decide compliance.
What does NFPA 520 cover?
NFPA 520 is the Standard on Subterranean Spaces. NFPA’s page states that it provides minimum requirements for the design, operation, and maintenance of developed subterranean spaces for safety to life and property from fire and similar hazards, for spaces developed for public assembly, business, industrial, or other uses.
NFPA’s official NFPA 520 page identifies the 2026 edition as current when checked on October 10, 2026. Confirm the edition, local amendments, and project scope that actually govern the work. The publisher’s newest edition does not establish local adoption.
Subterranean spaces still answer to the building code and the life safety requirements in the NFPA 101 guide. Smoke control design often follows the NFPA 92 guide. Record how the authority classifies the space and which documents govern before comparing.
Gather the underground layout and its life safety systems
Collect the overall plan of the subterranean space with its uses, the life safety and egress plans, the portal and shaft drawings, the smoke control drawings and narrative, the sprinkler and standpipe drawings, the fire alarm and emergency communication drawings, the emergency power drawings, the ventilation drawings, and the specifications.
Underground developments are often built out in phases. Upload the current overall plan with each tenant or phase package so egress and smoke control can be compared across the whole space.
Follow each underground area to the surface
| Review question | Sources to compare | Decision to record |
|---|---|---|
| Uses and areas | Overall plan, tenant plans, life safety plans | Confirm each area’s use and boundary is the same on the overall plan and the phase drawings. |
| Egress routes | Life safety plans, portal and shaft drawings | Trace each area’s path to the surface and find routes or exits that differ between sheets. |
| Smoke control | Smoke control drawings, narrative, ventilation plans | Check that smoke zones and fans in the narrative match the mechanical drawings. |
| Fire protection | Sprinkler and standpipe drawings, overall plan | Match the areas shown as protected with the current layout and uses. |
| Emergency power and communications | Electrical drawings, fire alarm and communication drawings | Ask the engineer to confirm which systems are on emergency power and that every source agrees. |
| Phasing | Phase plans, issue register, life safety plans | Identify phases whose egress or smoke control depends on construction not yet drawn. |
Road and rail tunnels follow different standards, covered in the NFPA 502 and NFPA 130 guides. The IBC Chapter 10 egress guide and storage facility projects raise related questions.
Example: a new tenant without a smoke zone
Hypothetical example. An underground business park adds a tenant space at the far end of an existing drift. The overall plan and the tenant plans show the new space, while the smoke control narrative and fan drawings still describe the drift as unoccupied storage.
The overall plan and tenant plans add an occupied space at the end of the drift, but the smoke control narrative and fan drawings still treat it as unoccupied storage. Please confirm the smoke control and egress for the new tenant and coordinate the drawings.
The design team updates the smoke control narrative and the life safety plans. Compliance is decided by the designers and the authority having jurisdiction.
Review a subterranean space with Groundbook
Upload the current project PDFs and relevant specifications to Groundbook. Identify the governing issues and add the applicable NFPA 520 reference from a copy you are licensed to use, where the license permits uploading it. State the edition, amendments, review area, and known exclusions in your instructions.
Compare the overall plan and uses, life safety and egress plans, portal and shaft drawings, smoke control drawings and narrative, sprinkler and standpipe drawings, fire alarm and communication drawings, emergency power drawings, ventilation drawings, and specifications. Flag uses, egress routes, smoke zones, protection, and emergency systems that differ between sources. Use the supplied NFPA 520 edition where applicable and cite both sources.
Groundbook links each potential finding to the sheets involved and the reference you uploaded.
Document review does not model smoke, calculate egress, or approve the space. Those decisions remain with the design team and the authority having jurisdiction.