Understanding Internal vs. External Overhaul on the Fireground

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Overhaul is one of the most overlooked yet operationally critical phases of firefighting on the fireground. It is often treated as the “cleanup” after the fire is out, but experienced firefighters know better. Overhaul is where fire either stays dead or quietly comes back to life. It is the operating firefighters final opportunity to eliminate hidden fire, confirm extinguishment, and prevent a rekindle that sends crews right back to the same address hours later. For many of us, I am sure we've been in that situation once or twice in our careers.

In modern fire operations, especially in lightweight construction, mixed occupancy buildings, and high heat-release fuel loads, overhaul is not optional. The question is not if we perform overhaul, but how we choose to do it. Whether this is done internally, externally, or a combination of both.

Understanding the difference between internal and external overhaul is essential for safe, efficient, and effective fireground decision-making.

What Overhaul Really Is

Overhaul is the systematic process of locating and extinguishing hidden fire after the main body of fire has been knocked down. Its purpose is simple, to eliminate hidden fire extension, prevent rekindle, confirm complete extinguishment and reduce future property and life risk.

But in the practical application, overhaul is where fire behavior meets building construction. Fire hides in void spaces, travels vertically and horizontally, and often survives suppression efforts if not aggressively sought out. A main reason why understanding building construction and its relation to fire behavior is a key attribute of a well-rounded firefighter and fire officer. You cannot have one without the other as highlighted in my book, "The 5-Tool Firefighter".

This is not passive work but rather it is controlled destruction with a purpose.

Internal Overhaul: Getting Inside the Problem

Internal overhaul is what most firefighters are familiar with. It involves crews operating inside the structure after knockdown to locate and extinguish remaining fire.

Operationally, this is where firefighters will being opening walls, ceilings, and floors, pulling insulation and debris and checking void spaces and cocklofts. During this time firefighters will use thermal imaging cameras to identify heat signatures looking to expose and extinguish hidden pockets of fire cutting off any extension to other rooms and floors.

Internal overhaul provides direct access to fire travel paths. It allows crews to physically trace the fire’s movement and confirm that no hidden pockets remain.

Advantages of Internal Overhaul

Internal overhaul is precise. When done correctly, it allows firefighters to follow the fire back to its source, ensuring complete extinguishment. It also provides immediate feedback of steam, heat, and visual confirmation guide decision-making in real time.

Risks of Internal Overhaul

With all advantages also comes with its own set of risks. Internal overhaul carries its own hazards:

  • Structural instability in weakened fire buildings

  • Heat stress and fatigue after heavy suppression work

  • Reduced air supply and SCBA endurance during extended operations

  • Hidden collapse potential in ceilings, floors, and roof assemblies

This phase requires discipline. The fire may be “knocked down,” but the environment is still active and dangerous.

External Overhaul: Working the Problem from the Outside

External overhaul is a more targeted approach that focuses on accessing fire from outside the structure. It is often underutilized, but in certain conditions, it can be the safer and more effective option.

Operationally, firefighters will begin opening exterior siding, soffits, and eaves and exposing roof edges or exterior void spaces. Crews will also be looking to remove exterior finishes to locate fire extension and begin coordinating ventilation with suppression efforts.

Instead of sending crews deep into potentially compromised structures, external overhaul allows firefighters to attack hidden fire from the perimeter.

Advantages of External Overhaul

External overhaul reduces exposure risk. It is especially valuable when the structure is unstable or compromised, interior access is limited or unsafe or fire has clearly extended into exterior void spaces. Another advantage to this type of overhaul is when staffing levels are limited but targeted work is still required. A scenario many fire departments are experiencing in today's world.

External overhaul allows for controlled, strategic removal of building materials without committing crews deep inside the hazard zone.

External overhaul is not a complete substitute for interior work and provides its own set of limitations. It may miss deep-seated interior fire in concealed spaces, provide limited visibility into fire travel paths or require follow-up interior confirmation in many cases. In this case, this type of overhaul works best as part of a coordinated strategy, not a standalone solution.

Choosing the Right Approach: Size-Up Drives Strategy

The decision between internal and external overhaul is not arbitrary. It should be based on continuous risk assessment and fireground intelligence.

Key factors include:

  • Structural stability and construction type

  • Location and behavior of fire extension

  • Time under fire conditions

  • Available staffing and resource levels

  • Weather conditions and environmental hazards

  • Incident objectives and operational tempo

Company officers and incident commanders must reassess conditions after knockdown. The building that was safe during suppression may not be ideal for prolonged interior overhaul. Understanding the impact fire conditions and firefighters working in and on top of the structure are vital areas to look at when determining overhaul tactics after fire suppression. 

Tools That Drive Effective Overhaul

Modern overhaul is increasingly technology-supported. Key tools include:

  • Thermal imaging cameras to identify hidden heat signatures

  • Hand tools such as hooks, pike poles, and axes for controlled opening

  • Gas meters for monitoring CO and hazardous atmospheres

  • Scene lighting for visibility in degraded environments

Technology supports decision-making, but it does not replace physical confirmation. Firefighters must still “open it up” when conditions demand it.

Safety: The Overhaul Phase Is Not Low Risk

One of the most dangerous assumptions on the fireground is that risk decreases once the fire is knocked down. In reality, overhaul introduces a different set of hazards:

  • Air quality degradation from CO and particulates

  • Fatigue accumulation after peak physical exertion

  • Structural degradation hidden beneath surfaces

  • Complacency after visible fire is gone

Accountability, communication, and rehab discipline remain critical. Crews operating in overhaul must maintain the same level of awareness as they did during initial fire attack.

Common Overhaul Failures

Many rekindles and callbacks can be traced back to poor overhaul practices, including superficial inspection of affected areas, overreliance on thermal imaging without physical verification, failing to open concealed void spaces or rushing overhaul to return companies to service. One of the biggest reasons for failures during overhaul isn't our actions but poor coordination between interior and exterior crews.  When overhaul is rushed, fire is not extinguished, it is temporarily hidden.

Best Practices for Effective Overhaul

Strong overhaul operations share common traits:

  • Slow, deliberate, and methodical search patterns

  • Aggressive confirmation of all potential extension paths

  • Coordinated internal and external operations when needed

  • Continuous communication between crews and command

  • Commitment to “nothing left burning” before clearing the scene

 The goal is not speed. The goal is certainty.

 Overhaul is not the end of the fire but it is the final control point. It is where discipline replaces urgency, and where attention to detail determines whether the incident is truly over or simply paused.

Internal and external overhaul are not competing tactics. They are complementary tools where smart, well-trained firefighters and departments understand when to go in, when to stay out, and how to combine both approaches to fully eliminate fire from the structure.

Because in the fire service, what you miss in overhaul is exactly what brings you back.

Until next time, work hard, stay safe & live inspired.

Reasons to Use a Thermal Imaging Camera on CO Alarm Calls

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Carbon monoxide alarm calls are often treated as routine responses, but they require the same disciplined size-up, hazard recognition, and risk management mindset as any other incident. A thermal imaging camera (TIC) provides firefighters with an additional layer of situational awareness by helping crews rapidly identify abnormal heat conditions, hidden hazards, and potential ignition sources that may be contributing to a CO event.

Using a TIC during CO investigations can improve operational efficiency, firefighter safety, and decision-making while also supporting documentation and homeowner education.

1. Identify Overheated Appliances

Many carbon monoxide incidents originate from malfunctioning appliances such as furnaces, boilers, water heaters, or stoves. A TIC allows crews to quickly identify abnormal heat patterns that may indicate:

  • Failing motors

  • Cracked or failing heat exchangers

  • Blocked exhaust systems

  • Overfiring burners

  • Overheating electrical components

Early identification can help isolate the source faster and reduce the risk of escalation.

2. Scan Flues, Chimneys, and Vent Systems

Blocked or damaged venting systems are a common cause of CO buildup inside structures. A TIC can help firefighters identify:

  • Overheated vent piping

  • Cold spots that may indicate blockages or restricted flow

  • Heat transfer where it should not be occurring

  • Improper venting conditions around chimneys or exhaust systems

This allows crews to better assess whether combustion gases are venting properly.

3. Detect Hidden Fire Conditions

Some CO alarm activations may be the first indication of a concealed fire or equipment failure. A TIC can assist in locating:

  • Smoldering electrical fires

  • Overheated wiring or outlets

  • Appliance malfunctions

  • Hidden hot spots inside walls, ceilings, or floors

This helps crews rule out or identify hidden fire extension before conditions worsen.

4. Improve Size-Up in Low-Visibility Environments

CO calls frequently occur at night, in basements, utility rooms, or other poorly lit areas. A TIC enhances operational awareness by providing:

  • Faster and safer navigation

  • Improved hazard recognition

  • Better visibility around obstacles or trip hazards

  • More accurate assessment of environmental conditions

This improves both efficiency and crew safety during the investigation.

5. Check for Heat Signatures Around Generators

Portable generators remain a major source of dangerous CO incidents. A TIC can help firefighters identify:

  • Improper generator placement

  • Running equipment hidden behind structures or inside garages

  • Overheating engines or exhaust systems

  • Heat signatures indicating recently operated equipment

This can quickly direct crews to a potential source of the CO problem.

6. Confirm or Rule Out Active Heating Sources

In some cases, CO alarms activate because of common household heating issues. A TIC can help determine whether appliances were recently operating, including:

  • Ovens or stovetops left on

  • Overheating space heaters

  • Improperly used fireplaces

  • Recently operated fuel-burning appliances

This helps narrow the investigation and identify potential contributing factors.

7. Enhance Firefighter Safety

CO alarm calls can appear routine, increasing the risk of complacency. Incorporating a TIC into the response helps improve overall firefighter safety by:

  • Increasing situational awareness

  • Identifying unseen heat sources or ignition hazards

  • Detecting abnormal conditions before they escalate

  • Reducing the likelihood of crews walking into hidden hazards

Using available technology reinforces a proactive rather than reactive approach.

8. Support Documentation and Customer Education

A TIC can also assist with post-incident communication and documentation. Visual findings help:

  • Explain malfunctioning appliances to occupants

  • Support evacuation or ventilation recommendations

  • Reinforce the need for utility or HVAC evaluation

  • Build trust through transparent communication

Providing residents with a visual understanding of the issue often improves compliance with safety recommendations.

Carbon monoxide alarm calls should never be viewed as “routine.” A thermal imaging camera enhances the investigative process by helping crews identify hidden hazards, malfunctioning appliances, abnormal heat signatures, and potential fire conditions more efficiently and safely. From improving low-visibility size-up to supporting firefighter safety and homeowner education, the TIC serves as a valuable tool that strengthens situational awareness and operational decision-making on every CO response.

Until next time, work hard, stay safe & live inspired.