Why grease fires start on a pellet grill

Flames inside the cook chamber, thick smoke from the tray, or a fire that starts below the rack: each of these points back to the same few causes. Here are the ones the sources name.

The cause makers name first: grease where it shouldn't be

Traeger's list of possible causes of a grill fire has two entries about dirt. They are an unclean grill and spilled grease.¹ A fire-safety page from San Bernardino County in the US makes the same point in its cooking safety advice: built-up grease can cause fires.²

Camp Chef says that if you don't clean the grill regularly, it can lead to airflow problems and to grease fires that can quickly escalate to house fires.³

So the first check is simple. Look at the tray, the plate under it and the bucket. The page on how grease travels shows what each part does.

Other causes on the list

1. The grill didn't light properly. Traeger says this is usually down to poor maintenance.¹
2. Ash build-up. Camp Chef says not emptying the ash cleanout leads to ash piling up and restricted airflow, which causes temperature swings and flameouts.³ That's not a grease fire on its own, but it's a sign the grill needs attention.
3. Foil that traps grease. Weber says creases in foil on its slide-out trays can build barriers that let grease pile up on the bottom tray. That builds the potential for grease fires and flare-ups.⁴ Weber is talking about its own grills there, so read what your maker says. The foil page has the detail: read it here.

Why grease burns differently

Fire experts treat cooking fats and oils as a class of their own. Under the European and Australian systems it's Class F, and under the US system it's Class K.⁵ The same page says water shouldn't be thrown on this type of fire, because it can cause the fuel to scatter and spread the flames.⁵ What to do is on What to do in a grease fire.

What the parts have to do with it

Each part along the grease path is a place where fat can stay instead of moving on. The tray is the first, the plate below it is the second, and the bucket is the last. If any of them is overloaded, the grease sits near the heat.

That's a reading of the sources, not a quote from them. Camp Chef's cleaning guide, for one, says the grease channel on the tray tends to get the most build-up.³ Check each one when you clean, and don't skip the ones you can't see from above.

Walking away

San Bernardino County's list of things you shouldn't do includes leaving your grill unattended.²

A quick check before each cook

• Is the tray clean, or crusted with old grease?
• Is the plate under it free of burnt-on build-up?
• Is the bucket close to full?
• Is the ash cleanout empty?

For how often to clean, see the cleaning-schedule page.

None of this replaces your manual. Follow the cleaning steps and warnings for your own grill.