The Difference between the Back-Up Line and the Second Attack Line

You’re responding as the second-due engine company at a working fire in a two-story, wood-frame dwelling with an attic (“2-A”). Upon arrival, you notice that fire is showing from the B/C corner window of the first floor. The first engine company has secured a water supply and is advancing an attack line toward the building. What are you going to do as the second-due engine? You have a couple options: You can stretch a back-up line (which you normally do as the second-arriving engine), or you can stretch a second attack line based on fire conditions and building construction.

Over the past few years, we’ve written several articles regarding attack line selection and effective hoseline deployment. This month, we’ll discuss the difference between stretching a back-up line and a second attack line.

The Most Important Priority
No matter which option you choose, the most important priority is to make sure the initial line stretched is making it to the fire. This may require your company to help the first-in engine get their line to the fire. Remember: Getting the first line operating on the fire makes things better for the occupants and for us! And since the first attack line puts out most of the fires we respond to, you must ensure that line is making good progress to the fire before you stretch additional lines. Depending on staffing, you may be able to simultaneously assist the initial line and deploy your hoseline.

We also recommend the second-due engine stretch the back-up or second attack line from their engine to provide redundancy in the system. As we’ve stated in the past, we’re strong advocates of every engine securing their own independent water supply when feasible. If the first engine has an issue related to mechanics, water supply or the driver/operator, the second engine can operate independently.

Back-Up vs. Second Attack
Now that we’ve secured a water supply and verified or assisted the first engine with the initial hoseline, what are we, as the second-due engine, going to do? Let’s get back to our options stated in the beginning and examine the differences between a back-up line and a second attack line.

The Back-Up Line
The back-up line is designed to be a safety line, therefore it should be positioned to protect the first-in engine in case they’re overrun by fire, lose water or have some other catastrophic issue with the line. It should be stretched through the same entrance as the first-in line and follow the same (or very similar) route to the fire. It should not get ahead of the initial line or create a situation where the hoselines oppose one another.

When advancing a back-up line, it’s important to remember not to overcrowd the first engine company. Instead, make sure to communicate with the first-in engine so they know your location and to ensure they’re OK. Note: This will be vitally important when we discuss the second attack line moving above the fire.

When selecting a back-up line, choosing the same size line as the initial line is acceptable only if the first line is appropriately sized for the volume of fire and the type of occupancy. Do not stretch a 1¾” line into a commercial occupancy just because the first-in engine made a mistake! Perform a size-up of the fire and the occupancy, and make the correct decision.

If, however, the first engine is using a 1¾” line on a compartmentalized structure, then selecting a 1¾” back-up line is acceptable because it will provide the same maneuverability as the initial line. If there’s any doubt that the first-in line will not be able to control the fire, then select a larger-diameter hoseline. Remember: The primary purpose of the back-up line is the safety of the initial attack line!

The Second Attack Line
There may be circumstances when stretching a second attack line is the correct tactic. If the amount of fire encountered is too great for one hoseline to extinguish, or fire is encountered on lower floors in multiple-story occupancies, then the second line should be used as an additional attack line. And just like the back-up line, the second line should be stretched using the same entrance and route to the fire as the first line, if possible, and the officers should coordinate the attack.

Unlike the back-up, however, the second line is not a safety line. Another difference between the two: selecting a hoseline that’s larger in diameter than the first-in engine is preferable.

Referring back to the original scenario, if the first-in line is making headway, the second engine may choose to advance the line to the second floor to cut off the fire extension. Note: It’s imperative to get a line above the fire in traditional, balloon- and platform- frame construction to prevent extension. No matter what action they take, the second engine must communicate with the first-in engine to ensure they’re getting water to the fire on the lower floor.

The first line must be advancing on the fire before going above; don’t pass up fire on floors below. In either case, an additional line must be stretched and staffed as a dedicated back-up line.

The Officer’s Tasks
The second-due engine officer must perform an independent size-up to determine the tactical function of the second hoseline. After the size-up, the second-due engine company decision matrix could look something like this:

  • Secure water supply
  • Assist first engine with initial line
  • Can first line control the fire? If no, advance a second attack line (larger diameter) coordinating with first engine (with back-up line by later-arriving company). If yes, stretch a back-up line of equal or greater diameter to support and protect the initial line.
  • Avenue for vertical extension? If yes, ensure first line controlling the fire and advance second attack line above the fire. Communicate with first-due engine (with back-up line by later-arriving company). If no, stretch a back-up line of equal or greater diameter to support and protect the initial line.

Both the back-up line and the second attack line play crucial roles on the fireground, but it’s important to understand when to use each one and which conditions dictate their use. The back-up line ensures the safety of firefighters on the first line, while the second attack line ensures that there will be extra “fire power” where needed. If used in the right ways, both of these lines will help facilitate a safe and successful outcome on the fireground every time.

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