Coldtrailer detects heat during mopup without bending over

The ColdTrailer panel, shown with a 12-inch ruler. Click to enlarge.

Today we are officially welcoming one of the most recent sponsors of Wildfire Today. The ColdTrailer can detect hot spots during mopup without a firefighter having to bend over or get on their hands and knees.

The story

In 1984 Jim Mundt, a McCall, Idaho based smokejumper, began thinking about a better way to find the last burning embers on a wildfire during mopup, the last task required before a fire could be declared out so the jumpers could abandon the fire, return to their base, and get back on the jump list. In 2000, working with his brother who was an electrical engineer, they developed the first prototype of a heat sensor mounted at the end of a pole. When the sensor detected heat, a speaker emitted a tone which changed as the temperature rose.

They worked on it for a couple of years, fine tuning the device and applying for a patent, but by then Jim was no longer a firefighter and the project languished.

Fast forward to 2017 when Patrick Wood, a crew member on the Los Padres Hotshots, came up with the same idea. When he researched the topic he found the Mundt brothers patent. The three of them began collaborating and are now making the ColdTrailer available to all wildland firefighters.

ColdTrailer, with a 12-inch ruler.

Field testing season

In 2018, 60 of the ColdTrailer MK 1’s were used by 20 crews, including 13 hotshot crews. The following are quotes from crewmembers on the Palomar Hotshots: “Saves our backs and hands from conventional cold trailing”,  “Very effective and easy to use cold trailing tool”, “Don’t have to bend over to hand feel the dirt” “The sensitivity was good and picked up even the smallest hotspots”, “Keeps you from potentially burning yourself”.

How it works

According to the company, the ColdTrailer functions very similarly to your hands and very differently from infrared technology. When barehanded cold trailing, any warmth detected is an indication of a possible hot spot so a firefighter must feel around to find the source of the heat.

With the ColdTrailer warmth is indicated by beeps. The faster the beeps the warmer it is getting. When the rate of beeps increases, the firefighter should spend a little more time checking that area for a real hot spot.

When the firefighter sweeps the probe through a hot spot the beeps get really fast, the LED flashes red, and a vibrating alarm pulses in the handle. The ColdTrailer can be used both to probe deep into root holes and also to sweep through the ash or duff right on the fire perimeter.

Why infrared is not a replacement for cold trailing

The company believes it is necessary to use a conduction-based heat sensor for cold trailing because infrared devices read surface temperatures, and ash is an insulator. Firefighters who use infrared as a replacement for cold trailing risk missing hot spots (unless in light fuels with a minimal ash layer).


The current version, the Coldtrailer MK. 2, is 4 feet 10 in. inches long when in use. Stored, the six sections fold like tent poles into a 12-inch package weighing less than a pound — 15 ounces. The six sections have a Kevlar cord strung through them keeping everything in the right order when it is folded. Inside the cord are two small electrical wires that run from the sensor to the control box. Assembling takes 15 to 20 seconds after you’ve done it once or twice.

Ergonomic design

The ColdTrailer has a strap that holds the six sections together when it’s folded. After the unit is assembled the strap is used to attach the upper end of the pole to the user’s arm while your hand grips it farther down on a foam pad. The two points of control provide leverage as the temperature-sensing end is dragged through ash on the ground.


One charge of the battery, which can be accomplished through a micro USB cable, lasts several months, according to the company. Lights indicate when the battery has 25% or 10% charge remaining. It shuts off after 10 minutes of not being used. There is a very, very small removable plastic plug which seals the charging port.


The Coldtrailer MK. II sells for $450. [There is a 15% discount if you buy 4 or more and a 25% discount if you buy 10 or more. They are available from the Supply Cache, Forestry Suppliers, and at the company’s website. International buyers should order from Forestry Suppliers or the Supply Cache. A 90 day risk-free trial is available for those who purchase through the company’s website.

Final analysis

Without the opportunity to use it on a fire I can’t say for certain that the ColdTrailer is a good investment, but if it works as intended, firefighters could cover ground more quickly during mopup while reducing the stress on their backs and knees during the tedious search for hotspots.

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Author: Bill Gabbert

After working full time in wildland fire for 33 years, he continues to learn, and strives to be a Student of Fire.