The coil is where all the physics of vaping actually happens. It is the component that converts electrical energy into heat, vaporises your liquid, and determines the character of every single puff you take — the draw tightness, the vapour volume, the flavour intensity and the nicotine delivery speed. Understanding coil types is not a topic reserved for enthusiasts: it is fundamental knowledge for anyone who wants to choose the right device and liquid combination from the beginning, or troubleshoot when something is not performing as expected.
The Basic Physics of Resistance Heating
A coil is a length of resistance wire wound around a wicking material, usually organic cotton. When battery current passes through the wire, its electrical resistance converts energy to heat through Joule heating — the principle described by P = I²R, where power dissipated increases with the square of current. The heated wire vaporises the liquid saturating the cotton wick. Capillary action then draws fresh liquid from the reservoir to replace what was consumed, keeping the system self-sustaining as long as liquid is available above the minimum wicking level.
Resistance is measured in ohms (Ω) and is the single value that determines how much power the coil draws from the battery at a given voltage, how much heat it generates, and consequently how much vapour it produces per puff. Lower resistance means higher current flow, higher heat, and higher vapour volume per draw. Higher resistance means the opposite: less current, less heat, less vapour, and a tighter draw profile. This is why coil resistance is the first number to understand when evaluating any vaping setup.
MTL Coils: The Cigarette Experience
Mouth-to-lung (MTL) describes a draw technique in which vapour is held briefly in the mouth before being inhaled into the lungs — exactly as one draws on a cigarette. MTL coils are engineered to complement this technique with specific physical characteristics:
- Resistance: typically 0.8Ω to 2.0Ω (sometimes called “above-ohm” or “+ohm”)
- Power range: 8–20W, resulting in low battery consumption and modest heat
- Airflow: restricted, producing a tight draw that closely mimics a cigarette
- Vapour production: low to moderate — discreet, not cloud-producing
- Nicotine compatibility: designed for 10–20 mg/ml freebase or nic salt liquids
- Flavour profile: precise and concentrated, with clear individual flavour notes
MTL coils are standard in pod systems (Vaporesso XROS, SMOK Nord, Uwell Caliburn families), pen-style vapes and most starter kits. They suit people transitioning from smoking, vapers who prioritise discretion and modest vapour, and the large majority of everyday vapers who are not cloud-chasing enthusiasts.
DTL Coils: Direct to Lung
Direct-to-lung (DTL) vaping involves drawing vapour directly into the lungs in a single deep inhale, bypassing the oral hold stage entirely. DTL coils serve this very different use case:
- Resistance: typically 0.1Ω to 0.5Ω (sub-ohm)
- Power range: 30–120W+, demanding high-capacity batteries
- Airflow: wide and unrestricted, enabling large-volume inhales
- Vapour production: high to very high — the cloud-producing end of the market
- Nicotine compatibility: 0–6 mg/ml only; higher concentrations cause overdose symptoms at these power levels
- Flavour profile: complex and layered, excellent for distinguishing multiple flavour components simultaneously
DTL setups are used in box mods with replaceable tanks and the advanced enthusiast segment. They are less suited to nicotine replacement use and more suited to established vapers interested in flavour complexity and vapour aesthetics.
Critical rule: MTL device + high nicotine (12–20 mg/ml). DTL device + low nicotine (0–6 mg/ml). Mixing these creates either nicotine overdose symptoms (high nic in sub-ohm) or unsatisfying craving management (low nic in MTL). The device determines the appropriate nicotine strength, not personal preference alone.
Wire vs Mesh: Why Mesh Has Won
Traditional wound coils created discrete hot spots where the wire contacted the wick. Mesh coils replaced the spiral with a flat, perforated strip of resistance material, dramatically increasing the surface area in contact with the liquid. The practical results are striking: faster and more even heating, better flavour from the very first puff with no break-in period required, significantly reduced risk of dry hits, and generally extended coil life across both MTL and DTL formats. Most manufacturers now produce mesh variants for all their coil ranges, and there is very little reason to choose a wire coil over mesh where both are available for the same device.
Coil Materials and Their Properties
- Kanthal (FeCrAl): Iron-chromium-aluminium alloy, industry standard for wattage-mode coils. Durable, consistent, inexpensive. Excellent starting material for beginners.
- Stainless Steel (SS316L): Compatible with both wattage mode and temperature control. Faster ramp-up than Kanthal, cleaner flavour profile, longer service life. The preferred choice for intermediate vapers.
- Nickel (Ni200): Temperature control mode only. Very low resistance, very fast ramp-up. Nickel sensitivity affects a meaningful minority of users — check before adopting.
- Nichrome (Ni80): Lower resistance than Kanthal for the same gauge and length. Popular with advanced builders. Not temperature-control compatible.
Temperature Control: The Underused Feature
Temperature control (TC) mode uses coil materials whose resistance changes predictably with temperature (a measurable TCR — Temperature Coefficient of Resistance). The device monitors resistance change in real time and limits power before the coil exceeds a set temperature. The practical benefits are substantial: dry hits are prevented entirely because the device cuts power before the cotton can scorch, coil life extends significantly, and the flavour character stays consistent from the first puff to the last drop of liquid. TC mode requires a compatible coil material (SS316L, Ni200 or Titanium) and a mod that supports TC. It remains dramatically underused by the mainstream market despite being one of the most genuinely useful features available on mid-range hardware.
Choosing the Right Coil for Your Setup
The right coil choice follows directly from device type and usage context. Former smokers using vaping as a cessation tool should use MTL coils at 1.0–1.8Ω, matched with nic salt liquid at 20 mg/ml — this combination most closely replicates the cigarette experience while minimising nicotine delivery risk. Established vapers seeking flavour complexity who have moved beyond active cessation should explore 0.2–0.4Ω mesh DTL coils with 3–6 mg/ml freebase liquid. Never purchase a device without first confirming which coil resistances it supports and that those resistances are compatible with your intended nicotine concentration.