E-liquid devices & coils: what the numbers actually mean

First, separate the three main parts

The battery unit supplies power. The pod or tank holds e-liquid. Inside it, a heating element and absorbent wick form the coil assembly: the wick holds liquid near the element, which heats it to create an aerosol. “Vapor” is the common term, but it is not simply water vapor. [1]

A tank typically uses a threaded 510 connection; a pod usually has a connection made for a particular device. A connection that physically fits still does not prove that the device supports the tank’s power requirements or coil resistance. [2]

Mesh versus wire: the heating element’s shape

A conventional wire coil uses a wound wire. A mesh coil uses a perforated strip or sheet. Both heat liquid held in a wick. Mesh describes the heating surface, not whether the coil fits a device or how much power it needs. [1]

A replaceable coil head packages the element and wick together. A built-in pod coil stays inside the pod. Check your manual before attempting removal: “refillable” does not automatically mean the coil is separately replaceable.

Ohms and watts are different numbers

Ω means ohms, the unit of electrical resistance. W means watts, the unit used for power. Lower-resistance coils are often designed for higher power, while higher-resistance coils often use less power. These are tendencies, not universal settings. [1]

“Sub-ohm” means resistance below 1.0 Ω. It does not identify a specific draw style or tell you which wattage to use. Read the range printed on the exact coil or its packaging. For example, Aspire lists its BP 0.3 Ω coil at 30–40 W. That range belongs to that coil, not every 0.3 Ω coil. [3]

Matching resistance numbers do not make two coils interchangeable. Check the device or tank model, the supported coil series and the exact variant.

MTL, RDL and DTL describe the draw

MTL means mouth-to-lung: a tighter draw, first into the mouth and then the lungs. RDL means restricted direct-lung: a more open draw with some restriction. DTL means direct-to-lung: an open draw typically associated with higher power. Airflow and coil design both matter; resistance alone does not define the experience. [4]

The liquid has to suit the hardware

PG (propylene glycol) is thinner; VG (vegetable glycerin) is thicker. A high-VG blend needs a wicking design that can supply it to the heating element. A liquid that is too thick for a particular coil can struggle to replenish its wick. Follow the liquid compatibility guidance for the device. [5]

Nicotine salt and freebase describe nicotine formulations, not coil types. The concentration on the bottle matters as well. Do not assume a high-strength liquid intended for a low-power pod is suitable for a high-output tank. Innokin specifically advises against high nicotine concentrations with DTL coils. [5]

Why a new coil can taste burnt

Priming means letting the wick become saturated before heating it. For removable coils, follow the manufacturer’s wetting, installation and waiting instructions. Innokin’s maintenance guide specifies wetting exposed wicking holes, filling the reservoir and allowing 10 minutes for saturation. That is manufacturer guidance, not a universal timer for every pod. [6]

On an adjustable device, begin at the low end of the coil’s specified range. Keep liquid above the wick openings and allow time between draws for the wick to replenish. Firing a dry wick or using excessive power can damage it. [6, 7]

When to replace a coil—and what a leak means

There is no guaranteed calendar lifespan. Liquid residue, power and frequency of use affect coil life. Persistent burnt taste or a marked decline in flavor can mean replacement is due. Adding liquid cannot repair a scorched cotton wick. [1, 7]

Gurgling or leaking alone does not prove the coil is worn out. Check the manual for correct seating, fill limits and seal inspection before replacing parts. If the device displays a coil error, stop and consult its troubleshooting instructions rather than repeatedly firing it.

For a built-in coil, replace the pod as directed. For a removable coil, replace only with an explicitly compatible head. Do not dismantle a sealed pod or try to rebuild a factory coil.

The details worth keeping

Keep a photo of the device or tank model, coil-series name, resistance and printed wattage range. Save the manual and the liquid label too. Those details make a compatibility check far more reliable than “it looks like the old one.”