Confined Space Design Flaws and Their Lethal Legacy

Introduction: Confined Spaces- Invisible Killers in Industrial Design

Confined spaces- pits, tanks, vessels, ducts, silos, and tunnels- are essential components of industrial infrastructure. Yet, these spaces often carry an inherent contradiction: while they serve practical engineering and operational purposes, their design frequently disregards the safety of the people who must enter them. Every year, dozens of workers die in confined spaces, and hundreds more suffer debilitating injuries or exposure due to flawed design.

Despite evolving regulations, awareness campaigns, and incident investigations, one pattern emerges again and again: the root of many confined space incidents lies not in worker behaviour, but in the original design itself. This article explores the critical design in many confined spaces- examining how engineering decisions create risk, and how better design can prevent tragedy.

1. Defining the Confined Space and Why Design Matters

Confined spaces are not merely tight or awkward places. In safety terminology, whilst there are various definitions depending on your jurisdiction, generally speaking, they are spaces that meet three criteria:

1. Not designed for continuous human occupancy

2. Limited means of entry or exit

3. Likely to contain a hazardous atmosphere, engulfment hazard, or other physical risks

Examples include:

• Below-ground pits (stormwater, process trenches)

• Pressure vessels and boilers

• HVAC and ducting systems

• Storage tanks and silos

• Underground tunnels and culverts

While these spaces are built for flow, containment, storage, or routing, they are rarely designed with human intervention in mind. When inspection, maintenance, or emergency intervention becomes necessary, workers are thrust into environments hostile to life.

2. Pits – The Underestimated Death Traps

2.1 Common Pit Configurations

Pits often exist in wastewater treatment, energy, manufacturing, and food processing. They can be open, covered, vertical, sloped, or ladder-accessible.

2.2 Key Design Flaws

• Single-point vertical access: Often with a single ladder or narrow access chute, making rescue extremely difficult.

• No ventilation design: No inbuilt provision for mechanical or natural airflow.

• Inadequate sump and drainage design: Accumulation of vapours or water due to poor sump location or drainage gradients.

• Low lighting and line-of-sight issues: Workers descend out of view of surface observers.

• Materials and coatings: Some pits are lined with materials that emit toxic gases when degraded or heated.

2.3 Real-world Incidents

• Worker dies in stormwater pit during cleaning- oxygen-deficient atmosphere not identified.

• Two rescuers were killed trying to retrieve a co-worker from a chemical sump with no breathing apparatus- a pit designed with no second exit or lifting anchor points.

3. Vessels – Complex Volumes with Lethal Legacies

3.1 The Shape Problem

Most vessels are cylindrical or spherical- great for pressure distribution, poor for human entry. The internal geometry often causes:

• Dead zones where gases settle

• Echo chambers that distort sound during emergency communication

• Slippery curved surfaces that complicate movement or rescue

3.2 Design Flaws in Vessels

• Manholes too small for stretcher access

• No anchor points inside or outside for fall protection

• Lack of internal ladders or footholds

• No provision for gas detection probe access

• No redundancy in ventilation pathways

3.3 Thermal and Chemical Hazards

Vessels are often used to store or react chemicals, increasing risks:

• Heat retention due to wall thickness

• Residual chemical vapours due to poorly designed wash-out systems

• Lack of temperature or pressure monitoring for entries

3.4 ICAM-Inspired Case Studies

Applying ICAM to major vessel incidents has repeatedly shown latent conditions, such as:

• A pressure vessel cleaned quarterly with no ventilation ports, requiring spot-entry by workers

• Designs omitting fall arrest tie-offs inside vessels, placing reliance on temporary scaffolds

• Hazardous materials stored in vessels with no coating or structural lining specified to resist corrosion

4. Ducts – Routes for Air, Not for People

4.1 Types of Ducting That Become Confined Spaces

• HVAC systems in high-rise buildings

• Flue gas ducts in power stations

• Slurry transport ducts in mining

• Process air return ducts in chemical plants

4.2 Design Neglect and Risks

• Sharp turns and angles: Impossible to navigate during rescue

• Flexible ducts not meant to support human weight

• Ducts with varying diameters or mechanical pinch points

• No flanged inspection panels for visual checks

• Insulation materials that emit toxic vapours when heated or degraded

4.3 The Movement Trap

Ducting often lacks consideration for:

• Movement space (workers must crawl, stoop, twist)

• Exit routes (no reverse travel if blockage occurs)

• Communication (no line of sight, no sound carry)

• Confined space monitoring equipment placement

4.4 Fire and Fume Hazards

Dust, insulation fibres, and chemical residue build-up can lead to:

• Flash fires during hot work

• Inhalation of harmful particulates

• Overpressurisation during system startup

5: What ICAM Reveals- Latent Design Conditions and Normalised Deviance

ICAM (Incident Cause Analysis Method) enables us to go beyond "worker error" and identify latent conditions- the hidden, often long-standing issues embedded into systems.

In confined space incidents, ICAM typically surfaces the following design-linked root causes:

• Design assumptions: “No one will ever need to enter this space.”

• Unclear specifications: Procurement teams are choosing lower-cost vessels without internal safety fixtures.

• Engineering oversights: CAD software optimising for volume, not safety.

• Organisational priorities: Schedule pressure is driving the use of vessels/pits without full safety reviews.

Normalised deviance becomes visible in operations that routinely bypass confined space protocols due to poor design:

• Opening duct hatches mid-operation

• Entering vessels solo due to access time constraints

• Using non-rated access points for pit entry

6: Regulatory Blind Spots and Loopholes

While many jurisdictions enforce confined space entry procedures (e.g., permits, gas testing, standby observers), few mandate design standards for confined spaces before they're built.

6.1 The Missing Design Standards

• AS 2865: Confined Spaces (Australia) focuses on entry procedure, not design.

• OSHA 1910.146 (US) defines permit-required spaces but doesn’t dictate physical design.

• ISO 45001 refers to hazard elimination, but not proactive confined space design.

This regulatory lag allows dangerous designs to be:

• Imported through overseas manufacturing

• Created in-situ with no engineering sign-off

• Passed through handovers with no maintenance plan for safe access

7: Engineering for the Living- Safer Design Principles

Safety by design isn’t new; it just needs to be enforced at the drawing board.

7.1 Design Interventions for Safer Pits

• Dual access ladders

• Fixed tripod/davit anchor systems

• Integrated gas sampling ports

• Sloped floors to prevent fluid buildup

• Remote camera access for inspections

7.2 Vessel Redesign Elements

• Full-body entry ports (18” minimum)

• Anchor rings inside and outside

• Dedicated ventilation ducts—not reused process lines

• Sloped bases with full washout capability

• Monitoring sensors that link to confined space dashboards

7.3 Ducting Redesign for Human Access

• Flanged access doors every 3–5 meters

• Uniform duct size to allow egress

• No pinch-point transitions

• Line-of-sight lighting strip integration

• Low-toxicity insulation and coatings

8: Innovations in Technology- Design and Retrofit Solutions

8.1 3D Design Reviews and Simulations

Modern design tools (e.g., BIM, AutoCAD Civil 3D) can simulate:

• Human ingress/egress

• Flow behaviour of gases

• Rescue extraction paths

8.2 Robotic and Remote Entry Solutions

• Crawler robots for duct inspection

• Drone-based vessel scanning

• Remote gas sensors that eliminate the need for physical entry

8.3 Retrofitting for Safety

Even old infrastructure can be upgraded:

• Add external anchor points and man-rated winch mounts

• Install permanent lighting and ventilation ports

• Use liners and coatings that resist toxic vapour accumulation

9: Cultural Change- From Compliance to Design Thinking

Workplaces must adopt a design-first mindset. Safety culture cannot rely solely on PPE, permits, or toolbox talks if people are being asked to enter inherently unsafe spaces.

9.1 Who Should Drive the Change?

• Engineers and designers- trained in human-centred confined space design

• Procurement and contracts teams- mandating safety features as non-negotiable

• Leaders and supervisors- questioning legacy equipment, not just behaviour

• Regulators- expanding codes to mandate safer designs

Conclusion: Safer Spaces Begin on the Blueprint

Confined spaces kill- not because workers make mistakes, but because they are often forced into spaces never meant to be entered safely in the first place. Every pit, vessel, and duct holds the potential for life-threatening exposure, entrapment, or tragedy- but this can be mitigated through deliberate, human-focused design.

As ICAM investigations show us time and again, the decisions made at the design stage ripple throughout an asset's entire lifecycle. It's time those decisions prioritise not just structural integrity and operational efficiency, but human survivability.

Call to Action: Building a Confined Space Design Standard

To truly prevent confined space fatalities, the industry must unite to create and adopt a Confined Space Design Standard- one that includes:

• Minimum safe access dimensions

• Mandated rescue access and anchor points

• Integrated remote inspection technologies

• Ventilation and lighting infrastructure

• Lifecycle risk assessments integrated into handover documentation

Safety shouldn't be an afterthought. It should be built into the steel, poured into the concrete, and drawn in from the very first draft.