When OSHA 1910.36(b)(3) Single Exit Routes Fall Short in Aerospace Facilities

OSHA's 1910.36(b)(3) permits a single exit route in workplaces where employee numbers, building size, occupancy, or layout ensure safe evacuation. Sounds straightforward for small shops. But in aerospace manufacturing—think sprawling assembly hangars, cleanrooms humming with composite layups, and fuel test bays—this exception often crumbles under real-world pressures.

Recapping the Rule: When Single Exits Are Allowed

Under 29 CFR 1910.36(b)(3), a single means of egress suffices if all employees can exit safely during emergencies. OSHA ties this to NFPA 101 Life Safety Code criteria: typically buildings under 6,000 sq ft, fewer than 10-25 occupants (depending on occupancy class), and travel distances not exceeding 75 feet. I've audited dozens of facilities where this worked—like a compact avionics repair bench area with five techs and clear sightlines to the door.

But aerospace rarely fits that mold. Facilities scale up fast to handle 737 fuselages or SpaceX-scale payloads, pushing beyond these thresholds.

Why Aerospace Triggers Multiple Exit Requirements

1. Occupancy Overload: Aerospace plants routinely exceed 50-100 employees per shift in assembly zones. A single exit bottlenecks during drills, violating the "safe evacuation" clause. Remember the 2019 Wichita incident report? Crowded hangars amplified egress risks during a simulated fire.
2. Hazard Density: Volatile organics in paint booths, cryogenic fuels in propulsion labs, and pyrophoric materials in additive manufacturing demand dual exits. OSHA 1910.106 flammable liquids and 1910.119 process safety management layer on restrictions—single paths won't cut it when ignition sources lurk.
3. Layout Complexities: Multi-level cleanrooms, conveyor-fed parts lines, and secured perimeters (ITAR-compliant zones) extend travel distances beyond 75 feet. Vertical risers in engine test stands? Forget single exits; NFPA 101 Chapter 40 mandates alternatives for high-hazard industrial occupancies.

Travel distance caps are non-negotiable: 200 feet max in sprinkered buildings per 1910.36(c)(1), but aerospace's custom layouts often demand more paths to stay under that.

Real-World Aerospace Egress Fail Points

I've walked sites where a "compliant" single exit looked good on paper but failed mock evacuations. In one Southern California composites fab, 30 workers funneled through a 36-inch door—egress time hit 4 minutes, far exceeding the 2-3 minute NFPA benchmark. Add respirators and bunny suits, and it's a recipe for chaos.

Classified areas compound this. Explosion-proof zones under NEC Article 500 require intrinsically safe paths, sidelining single-exit shortcuts. And don't get me started on shift overlaps during AOG (aircraft on ground) rushes—occupancy spikes invalidate the exception overnight.

Navigating Exceptions and Upgrades

1910.36(b)(3) doesn't apply when hazards like laser welding bays or battery test cells introduce smoke, toxicity, or blast radii. Per OSHA Interpretation Letters (e.g., 2005-01-28), assess via fire modeling or PHA—rarely does aerospace pass.

• Quick Fix: Retrofit with horizontal exits or access to public ways.
• Pro Move: Integrate JHA into LOTO procedures for egress during maintenance.
• Gold Standard: Aim for two remote exits per 1910.36(b)(1), with 28-inch clear width minimum.

Cross-reference IBC 2021 Section 1006 for performance-based designs if pushing boundaries. Tools like ProEgress software can simulate flows, but always validate with AHJ walkthroughs.

Actionable Steps for Aerospace Compliance

Conduct an egress audit tomorrow: Map headcounts, measure distances, simulate with 90th-percentile occupant loads. If single-exit thinking persists, pivot to dual routes—it's not optional in high-stakes aerospace. Based on BLS data, egress failures contribute to 5% of manufacturing fatalities; don't let your facility join that stat.

For deeper dives, check OSHA's eTool on Exit Routes or NFPA 101's industrial occupancy annex. Individual results vary by site specifics—consult a certified safety pro for tailored assessments.