Stack (Chimney) Construction JHA (Job Hazard Analysis / Activity Hazard Analysis)
Updated 2026-06-23
A Stack (Chimney) Construction JHA (Job Hazard Analysis / Activity Hazard Analysis) is the plan that keeps the crew building a power plant stack from falling from the extreme height, being struck by objects falling from far above, or trapped by the difficult access and rescue. Stack (chimney) construction builds the tall exhaust stacks that vent flue gas from power plants — among the tallest and most extreme-height structures on a project, combining the extreme working height, the severe falling-object hazard down the tall structure, and the difficult access and rescue. This guide walks through building a Stack (Chimney) Construction JHA that names the extreme-height, falling-object, and access hazards and assigns the fall-protection, dropped-object, and rescue controls that hold up in the field.
Why stack (chimney) construction needs its own JHA
Stack (chimney) construction builds the tall exhaust stacks — the concrete or steel chimneys (often with an inner liner/flue) that vent flue gas from boilers and HRSGs, among the tallest structures on a power plant, sometimes many hundreds of feet tall. Construction uses slipforming or jumpforming for concrete stacks, or lift/jack methods for steel, plus the liner installation, working at continuously increasing extreme height. The hazards are dominated by the extreme height. The extreme working height (stacks are among the tallest structures — the work occurs at extreme and increasing height, where falls are catastrophic and the height itself is a severe hazard). The falling-object hazard (objects, tools, or materials dropped from the extreme height gain enormous energy and are lethal to anyone below — a severe hazard on tall stacks). The difficult access and rescue (access to the extreme height is by hoists and climbing, and rescue from the top of a stack is difficult and specialized). And the slipform/jumpform operation and weather. The extreme height, the falling-object hazard, and the difficult access/rescue justify a dedicated JHA.
Breaking stack (chimney) construction into steps
The steps for a Stack (Chimney) Construction JHA follow the stack:
- Establish the foundation and base
- Set up the slipform/jumpform or lift system
- Construct the stack shell at increasing height
- Establish and maintain fall protection at all heights
- Control falling objects to workers below
- Install the liner/flue
- Manage access, hoisting, and rescue
- Complete and top out
Each step carries a hazard, and the extreme height, the falling-object hazard, and the access/rescue are where the most serious risks concentrate.
The hazards step by step
Extreme working height
Stacks are among the tallest structures, and the work occurs at extreme and continuously increasing height, where falls are catastrophic and the height itself is a severe hazard. The controls are comprehensive fall protection at all heights (100% tie-off, guardrails on the work platforms, the slipform/jumpform deck protection), certified high-work crews, safe work platforms, and managing the extreme and increasing height. The extreme height is the defining, pervasive hazard. (These follow the working-at-height fundamentals.)
Falling-object hazard
Objects, tools, or materials dropped from the extreme height of the stack gain enormous energy over the fall and are lethal to anyone below — a severe hazard on tall stacks, and the tall, narrow structure means the base area is the impact zone. The controls are rigorous dropped-object prevention (tool tethering, securing all materials and tools, toe boards and netting on platforms, no loose objects at height), exclusion zones at the base and around the stack (keeping personnel out of the drop zone), controlled hoisting of materials, and managing the falling-object hazard. The falling-object hazard is severe given the height. (These follow the dropped-object fundamentals.)
Difficult access and rescue
Access to the extreme height is by construction hoists and climbing, and rescue from the top of a stack is difficult and specialized — a worker needing rescue at the top of a tall stack is far from the ground and hard to reach. The controls are safe construction hoists and access, a specialized high-angle/at-height rescue plan and capability for the extreme height (rescue from a stack requires planning and equipment), communication, and emergency provisions at height. The difficult rescue makes the rescue plan critical.
Slipform/jumpform operation and weather
The slipform/jumpform operation (the continuously moving form, the concrete placement at height) and the weather (wind increases with height, and the exposed work) carry their hazards. The controls are the slipform/jumpform operational controls, wind/weather limits and monitoring (wind is stronger at height), and managing the continuous operation.
A simple Stack (Chimney) Construction JHA structure
| Step | Hazard | Control | Standard |
|---|---|---|---|
| Construct at height | Extreme-height fall | Comprehensive fall protection, 100% tie-off, platform protection | OSHA 1926.501 |
| Control dropped objects | Falling-object fatality | Tool tethering, secure materials, toe boards/netting, base exclusion | OSHA 1926.759 |
| Slipform/jumpform | Form / concrete / height | Slipform operational controls, deck protection | ACI 306 |
| Manage access | Access / hoisting | Safe construction hoists, controlled hoisting | OSHA 1926.552 |
| Plan rescue | Difficult rescue | Specialized at-height rescue plan and capability | OSHA 1926.502 |
| Manage weather | Wind (higher at height) | Wind/weather limits and monitoring, cease in high wind | manufacturer |
Extreme height, falling objects, and difficult rescue
A Stack (Chimney) Construction JHA is defined by the extreme height and its consequences: the fall hazard, the falling-object hazard, and the difficult rescue. The extreme height makes comprehensive fall protection at all heights, certified crews, and safe platforms paramount, because falls are catastrophic. The falling-object hazard is severe — objects dropped from the extreme height gain enormous energy and are lethal below — so rigorous dropped-object prevention (tethering, securing, netting) and base exclusion zones are essential. The difficult rescue — rescue from the top of a tall stack is specialized and hard — makes a specialized at-height rescue plan and capability critical. A JHA built on comprehensive fall protection, rigorous falling-object control, and a specialized rescue plan addresses the hazards that define stack construction.
From the field: what actually goes wrong
In fourteen years across federal, heavy civil, and industrial projects, stack construction is among the most extreme-height work on any project — stacks are among the tallest structures, sometimes many hundreds of feet tall, and the work climbs continuously higher. The extreme height dominates everything: falls are catastrophic, and comprehensive fall protection at all heights, certified high-work crews, and safe platforms (with the slipform/jumpform deck protection) are paramount. The extreme, increasing height is the defining condition of stack work, and every control flows from it.
The falling-object hazard and the difficult rescue are the two extreme-height consequences that stack work makes especially severe. An object, tool, or piece of material dropped from the top of a tall stack gains enormous energy over the long fall and is lethal to anyone below — and the tall, narrow structure means the base is the impact zone. So rigorous dropped-object prevention is essential: tool tethering, securing all materials and tools, toe boards and netting on platforms, no loose objects at height, and exclusion zones keeping personnel out of the drop zone at the base. And rescue is genuinely difficult — a worker needing rescue at the top of a stack is far from the ground and hard to reach, so a specialized at-height rescue plan and capability, with the right equipment, is critical, not optional. On the projects I have run, the slipform/jumpform operation and the wind (stronger at height) add their hazards. The JHA built on comprehensive fall protection, rigorous falling-object control, and a specialized rescue plan is the one that protects the stack crew.
The bottom line
A Stack (Chimney) Construction JHA names the extreme-height, the falling-object, and the access hazards with specific controls — comprehensive fall protection at all heights for the extreme, increasing height, rigorous dropped-object prevention with base exclusion zones for the severe falling-object hazard, and a specialized at-height rescue plan for the difficult rescue. The extreme height, the falling-object hazard, and the difficult rescue are the defining hazards. The JHA that manages them is the one that protects the crew.
Frequently asked questions
Why is extreme height the defining stack hazard?
Stacks are among the tallest structures on a project, sometimes many hundreds of feet tall, and the work occurs at extreme and continuously increasing height, where falls are catastrophic and the height itself is a severe hazard. Controls are comprehensive fall protection at all heights (100% tie-off, guardrails, slipform/jumpform deck protection), certified high-work crews, safe work platforms, and managing the extreme and increasing height.
Why is the falling-object hazard so severe on stacks?
Objects, tools, or materials dropped from the extreme height of the stack gain enormous energy over the long fall and are lethal to anyone below, and the tall, narrow structure means the base area is the impact zone. Controls are rigorous dropped-object prevention (tool tethering, securing all materials and tools, toe boards and netting, no loose objects at height), exclusion zones at the base and around the stack, controlled hoisting, and managing the falling-object hazard.
Why is rescue difficult on a stack?
Access to the extreme height is by construction hoists and climbing, and rescue from the top of a tall stack is difficult and specialized — a worker needing rescue at the top is far from the ground and hard to reach. Controls are safe construction hoists and access, a specialized high-angle/at-height rescue plan and capability for the extreme height, communication, and emergency provisions at height.
How does weather affect stack construction?
Wind increases with height, so the exposed work at the top of a tall stack faces stronger winds than at ground level, and the slipform/jumpform operation is weather-sensitive. Controls are wind/weather limits and monitoring (accounting for the stronger wind at height), ceasing work in high wind, and managing the continuous slipform/jumpform operation around the weather.
Related JHAs
- Working at Height JHA — the extreme-height fundamentals
- Formwork Installation JHA — the slipform/jumpform formwork
- Steel Erection JHA — the structural erection and dropped-object controls
- Heat Recovery Steam Generator (HRSG) Installation JHA — the HRSG the stack vents
Written by Mustafa Tok, CSP, ASP, CHST — OSHA Authorized Outreach Trainer with 14+ years of international construction safety experience across federal, heavy civil, and industrial projects.