Courthouse Holding Cell HVAC Systems

Overview

Courthouse holding cells require specialized HVAC systems that balance security, occupant health, and operational reliability. These temporary detention spaces demand ventilation rates exceeding standard occupancy requirements while incorporating tamper-resistant components and complete separation from public building systems.

Ventilation Requirements

Air Change Rates

ASHRAE Standard 62.1 and American Correctional Association (ACA) standards establish minimum ventilation requirements for holding cells. The ventilation rate must account for high occupancy density and limited egress.

Required ventilation rate:

$$Q = \max(n \cdot V, P \cdot R_p)$$

where:

• $Q$ = required airflow (CFM)
• $n$ = air changes per hour (ACH)
• $V$ = cell volume (ft³)
• $P$ = number of occupants
• $R_p$ = per-person ventilation rate (CFM/person)

For courthouse holding cells:

$$Q_{cell} = \max\left(12 \cdot \frac{V}{60}, P \cdot 20\right)$$

Standard design parameters specify 12-15 ACH or 20 CFM per occupant, whichever is greater.

Ventilation Rate Table

System Design Principles

Air Distribution Separation

Holding cell HVAC systems must operate independently from public courthouse areas to prevent:

1. Contaminant migration from detention spaces to public areas
2. Security breaches through shared ductwork
3. Cross-contamination between cells

graph TB
    subgraph "Dedicated Holding Cell System"
        AHU[Dedicated Air Handler<br/>100% Outside Air]
        HEPA[HEPA Filtration<br/>MERV 14 minimum]
        Supply[Tamper-Proof Diffusers]
        Cell1[Holding Cell 1<br/>-0.03 to -0.05 in. WC]
        Cell2[Holding Cell 2<br/>-0.03 to -0.05 in. WC]
        Cell3[Holding Cell 3<br/>-0.03 to -0.05 in. WC]
        Exhaust[Dedicated Exhaust Fan<br/>with VFD]

        AHU --> HEPA
        HEPA --> Supply
        Supply --> Cell1
        Supply --> Cell2
        Supply --> Cell3
        Cell1 --> Exhaust
        Cell2 --> Exhaust
        Cell3 --> Exhaust
        Exhaust -.->|Exhausted to Atmosphere| Outside[Roof Discharge<br/>No Recirculation]
    end

    subgraph "Public Courthouse System"
        PublicAHU[Public Area AHU]
        Court[Courtrooms]
        Lobby[Public Lobby]

        PublicAHU --> Court
        PublicAHU --> Lobby
    end

    style Cell1 fill:#ffcccc
    style Cell2 fill:#ffcccc
    style Cell3 fill:#ffcccc
    style Exhaust fill:#ff9999

Pressure Control Strategy

Maintain negative pressure in all holding areas relative to adjacent spaces:

$$\Delta P = P_{adjacent} - P_{cell} = 0.03 \text{ to } 0.05 \text{ in. WC}$$

This pressure differential prevents odor migration and maintains directional airflow into detention spaces.

Odor Control Methods

Multi-stage approach:

1. High ventilation rates (12-15 ACH minimum)
2. 100% outside air supply (no recirculation)
3. Negative pressure maintenance
4. Activated carbon filtration in exhaust stream
5. Direct exhaust to atmosphere above roof level

Activated carbon bed sizing:

$$M_{carbon} = \frac{Q \cdot C \cdot t}{1000 \cdot \eta}$$

where:

• $M_{carbon}$ = carbon mass required (lbs)
• $Q$ = exhaust airflow (CFM)
• $C$ = contaminant concentration (ppm)
• $t$ = service life (hours)
• $\eta$ = removal efficiency (fraction)

Security Requirements

Tamper-Proof Component Specifications

Ductwork Routing

Critical design considerations:

1. No shared ductwork between holding cells and public spaces
2. Duct penetrations through security barriers require steel sleeves
3. Minimum duct gauge of 22 for concealed areas
4. Inspection access from secure corridors only
5. Grille bar spacing not to exceed 4 inches

flowchart LR
    subgraph SecurityZone["Secure Holding Area"]
        direction TB
        A[Air Handler<br/>Secure Mechanical Room]
        B[Supply Duct<br/>Above Security Ceiling]
        C[Cell Supply Grille<br/>Tamper-Proof]
        D[Cell Exhaust Grille<br/>Security Rated]
        E[Exhaust Duct<br/>Isolated Routing]
        F[Exhaust Fan<br/>Roof Mounted]

        A -->|Positive Pressure| B
        B --> C
        C -.->|Cell Airflow| D
        D -->|Negative Pressure| E
        E --> F
    end

    G[Outside Air<br/>Intake] --> A
    F --> H[Atmosphere<br/>Discharge Point]

    style SecurityZone fill:#ffe6e6
    style C fill:#ffcccc
    style D fill:#ff9999

Temperature Control

Maintain temperature within ranges specified by ACA standards:

Winter: 68-72°F Summer: 72-78°F

Temperature control must be:

• Non-adjustable by occupants
• Monitored remotely by facility staff
• Alarmed for out-of-range conditions

Control strategy equation:

$$T_{supply} = T_{setpoint} - \frac{Q_{sensible}}{1.08 \cdot CFM}$$

System Monitoring

Implement continuous monitoring for:

1. Supply airflow to each cell (±10% alarm threshold)
2. Exhaust fan status (failure alarm)
3. Pressure differential (loss of negative pressure alarm)
4. Temperature in each cell (out-of-range alarm)
5. Filter differential pressure (replacement indicator)

Design Checklist

• Dedicated air handler for holding cell zone
• 100% outside air supply (no recirculation)
• 12-15 ACH minimum ventilation rate
• Negative pressure maintained in all cells
• Tamper-proof grilles and components specified
• No ductwork shared with public areas
• Exhaust discharged to atmosphere
• Remote temperature monitoring installed
• Pressure monitoring with alarms
• Security grille bar spacing ≤ 4 inches
• All components accessible only from secure areas

References

• ASHRAE Standard 62.1: Ventilation for Acceptable Indoor Air Quality
• American Correctional Association (ACA): Performance-Based Standards for Adult Local Detention Facilities
• International Mechanical Code (IMC): Special occupancy requirements
• ASHRAE Handbook - HVAC Applications: Chapter on Justice Facilities