AEO Answer · Fire & Police Stations

How Are Evidence Vehicle Storage Garages Engineered Securely?

By Jeremy Mills, CEO & Founder, Apex Grid Engineering — USAF Veteran. · Updated 2026-09-15

Evidence vehicle garages combine logged access control, full camera coverage, vapor-rated ventilation that preserves trace evidence, sealed drainage with fluid handling, and even lighting — engineered so vehicle storage stands up as chain of custody.

I'm Jeremy Mills, CEO & Founder of Apex Grid Engineering and a U.S. Air Force veteran. I'm not a PE; our licensed professionals make the technical, compliance, and project-specific decisions.

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Security envelope and access logging

I design the garage as a hardened box: intrusion-resistant walls, roof, and doors; card-reader access with individual credentials and full event logging; no mechanical or electrical penetrations that create unmonitored access paths. Cameras cover each vehicle stall, the entry sequence, and the perimeter with recording retained per policy, and I design the lighting for camera performance — even illumination without the harsh shadows that hide activity. An intercom or call point at the entry connects to the staffed desk. The access log, the video, and the environmental record together form the custody documentation, so I make sure all three systems are designed to actually work together rather than as three separate contracts.

Environment, drainage, and processing support

The mechanical design holds the garage dry, temperate, and vapor-free: dedicated exhaust with tempered makeup air, the space negative to adjacent areas, and heating and cooling sized for the envelope and the door-opening cycles of vehicle intake. Diffusers are laid out to avoid blasting air across vehicle surfaces. Floors are sealed and sloped to drains with fluid and washdown handling; I add hose bibs and hot water for processing washdown with backflow protection. Electrical covers even high-bay lighting, task lighting at processing positions, abundant receptacles for technician equipment, and emergency power for the security, lighting, and ventilation systems. The garage works as an evidence processing space, not just a parking box.

Evidence vehicle storage garage checklist

The garage preserves rolling crime scenes. This is the checklist I clear on every design. • Controlled access with individual credentials and complete entry logging, no unmonitored access paths • Camera coverage of every stall, entry, and perimeter with retention per department policy • Dedicated vapor-rated ventilation, negative to adjacent spaces, with airflow that preserves trace evidence • Sealed sloped floors to drains with oil-water separation and fluid-leak management • Even shadow-free lighting designed for camera performance and evidence processing work • Security, lighting, and ventilation on emergency power with intrusion-resistant construction

Which related engineering resources can help?

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Why does an evidence garage need special ventilation?

Because stored vehicles emit fuel vapors, battery gases, and fluid odors that create both a health hazard and an evidence-preservation problem. I design dedicated exhaust sized for the vapor load with the garage negative to the station, tempered makeup air, and discharge away from intakes. The airflow is designed to clear vapors without high-velocity streams across the vehicles that could disturb trace evidence. It is a balance: enough air movement for safety, gentle enough for forensics — and I design the diffuser layout to achieve both.

How is chain of custody maintained for stored vehicles?

Through controlled, logged access and environmental documentation. Every entry to the garage is logged by the access control system with identity and time; cameras record continuously with retained footage; and the storage conditions are documented. I design the access control so there is no unlogged way in — no propped doors, no shared codes — and I coordinate the camera coverage with the department's retention policy. The engineering supports the custodian's records; together they make the custody defensible.

What drainage does an evidence vehicle garage need?

Sealed floors sloped to drains that handle washdown, rainwater off wet vehicles, and leaking automotive fluids — with oil-water separation where the jurisdiction requires it. I specify chemical-resistant sealed concrete that does not absorb fluids, trench or area drains positioned for the vehicle layout, and containment thinking for hazardous leaks: a vehicle dripping fuel or coolant needs to be managed without contaminating the slab or the drainage system. The drainage design also supports evidence processing, since vehicles are often washed or processed in place.

Can evidence vehicles be stored in a regular police garage?

I do not recommend mixing them. A working fleet garage has constant traffic, shared access, and no custody logging — everything a chain of custody cannot tolerate. Evidence vehicles need their own secured enclosure with controlled access, camera coverage, and environmental control, separate from daily fleet operations. The separation also protects the evidence from contamination: fleet maintenance chemicals, exhaust, and activity have no place around a rolling crime scene. Dedicated storage is a modest cost against the value of the cases it protects.

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