Air Gap and Airflow in a Collapsible Grill

How the space under a flat pack grill's coal bed affects airflow, heat on the surface below, and how to set up safely on a table or tailgate.

Fire needs air from below. A grill that sits flat on the ground with coals right on the floor tends to smother and to cook the surface it sits on. Collapsible grills solve this by raising the coal bed. Slot Grill calls the distance from the table to the bottom of the coal bed the air gap.

The makers say the air gap helps minimize radiant heat to the surface below, and the elevated firebox improves airflow. "Minimize" is the key word: it is still a live charcoal fire, and the surface under it still has to be non-combustible.

Using airflow to control heat

A lidless grill has no vents to adjust, so you control heat with fuel and placement:

• More coals, closer together = hotter.
• Spread coals out = cooler and longer-lasting.
• Leave an empty zone for indirect cooking; see two-zone fire.
• Empty old ash before each cook; ash blocks air.
• Wind acts like a bellows. Turn the grill or shield it; see wind and weather.

Safe surfaces

Good: bare soil, gravel, sand, concrete, pavers, a fire-safe pad. Not good: wood decks, plastic tables, vinyl, dry grass, truck bed liners or boat decks. If you must cook on a table, make it a metal or stone table with a heat-resistant pad, and keep the grill well clear of the edge.

The two Slot Grills at a glance

Figures from SlotGrill.com. For the full breakdown, see Compact vs Full Size.

Fire safety on any collapsible grill

• Outdoors only. Burning charcoal makes carbon monoxide, which you can't see or smell. Never use it in a garage, tent, camper, vehicle, boat cabin or under a roof or awning.
• Non-combustible, level ground. Soil, gravel, sand, concrete, pavers or a fire-safe pad.
• Clearance. Away from walls, vehicles, tents, overhanging branches and dry grass. Kids and pets kept back.
• Seated tabs. Check every tab is fully in its slot before you add fuel.
• Water and gloves at hand. Hot steel looks exactly like cold steel.
• Leave it alone until cold. Don't move or take apart a lit or warm grill.

Mistakes new flat pack owners make

1. Too much charcoal. A small firebox gets very hot. Start with half a chimney and add.
2. No cool zone. Without an empty end, a flare-up has nowhere to go.
3. Cooking on black coals. Wait for gray ash.
4. Old ash left in. It blocks airflow; empty it before every cook.
5. Heavy oil when seasoning. Thin coats cure; thick coats turn gummy.
6. Packing it warm. Wait until steel and ash are cold, every time.

Questions people ask