A vape works by using a small battery to heat a liquid into an aerosol that you inhale. There’s no fire, no tobacco, and no combustion involved. Instead, an electrical current passes through a tiny metal heating element, which gets hot enough to turn a few drops of liquid into a fine mist. That’s the basic principle behind every vape on the market, from slim disposables to chunky box mods.
What’s Inside a Vape
When researchers at UNSW in Australia pulled apart disposable vapes to see what was inside, they found the same core components that exist in every type of e-cigarette: a battery, a heating element, a wick, and a reservoir of liquid. Disposables also contain a pressure sensor (essentially a modified microphone) and a small LED light. That’s it. The entire device is surprisingly simple.
The battery is a small lithium cell that stores the energy needed to heat the coil. Even in disposable, non-rechargeable vapes, the battery inside is a standard lithium cell. In refillable devices, the battery is rechargeable and often makes up most of the device’s weight and size.
The reservoir holds the e-liquid. In disposable vapes, this is typically a plastic tube filled with absorbent foam material soaked in liquid, sealed with silicone endcaps. Refillable devices use a small tank or pod that you fill yourself. Sitting in the center of the reservoir is a wick, a strip of material (usually cotton or synthetic fiber) that draws liquid toward the heating element through capillary action, the same principle that lets a paper towel soak up a spill.
From Liquid to Aerosol
When you take a drag on a vape, the pressure sensor detects the change in airflow and signals the battery to send current to the heating element. Some devices skip the sensor entirely and use a manual button instead. Either way, the result is the same: electricity flows through a small metal strip or coil, and it gets hot.
Under normal use with a properly saturated wick, coil temperatures typically range from about 110°C to 185°C (230°F to 365°F). That’s enough to vaporize the liquid without burning it. If the wick isn’t fully saturated, which can happen during heavy use or when the tank is running low, temperatures climb much higher, anywhere from 145°C to over 300°C. This is what causes a “dry hit,” that harsh, acrid taste that signals the liquid is overheating or the wick itself is starting to scorch. A completely dry coil can spike past 1,000°C, though anyone who has experienced the taste of a dry hit stops inhaling long before it reaches that point.
Higher power settings heat the coil to higher temperatures, which produces more aerosol per puff. This is why adjustable-wattage devices let users control the intensity of their experience.
What’s in the Liquid
E-liquid has a small number of core ingredients: propylene glycol (PG), vegetable glycerin (VG), nicotine, and flavorings. PG and VG are both clear, slightly thick liquids approved for use in food and cosmetics. They serve different roles in a vape.
PG is thinner and carries flavor well. It’s also responsible for the “throat hit,” that slight catch at the back of your throat that mimics the sensation of smoking. In a study comparing different PG/VG ratios, participants consistently rated the highest PG concentration (70/30 PG to VG) as having a significantly stronger throat hit than a 50/50 blend or a VG-dominant liquid. VG is thicker and sweeter. It’s widely believed to produce bigger vapor clouds, though in the same study, participants didn’t actually rate cloud production differently across the ratios they tested.
Commercial e-liquids typically range from 70/30 PG/VG on the PG-heavy end to nearly 100% VG on the other. A 50/50 blend is the most common middle ground. The ratio you choose affects the thickness of the liquid, how it feels in your throat, and how quickly it saturates the wick.
How Nicotine Gets Absorbed
Most e-liquids contain nicotine, but not all nicotine is formulated the same way. The two main types are freebase nicotine and nicotine salts, and the difference comes down to chemistry that affects how they feel.
Freebase nicotine has a higher pH (around 8.9), which makes it more alkaline. At higher concentrations, it produces a harsh throat sensation that many people find uncomfortable. Nicotine salts are treated with an acid to lower the pH to around 6.6, making them smoother to inhale even at high concentrations. This is why most disposable vapes and pod systems use nicotine salts at concentrations of 20 mg/mL or higher, while freebase nicotine is more common in lower-strength liquids used with larger devices.
The chemistry also affects absorption. In nicotine salt solutions, roughly 98% of the nicotine molecules carry an electrical charge (they’re “protonated”), which makes them less likely to cross cell membranes quickly. Freebase nicotine has a much lower proportion of charged molecules, around 17%, allowing it to diffuse into tissue more readily. In practice, the higher concentrations in salt-based liquids tend to compensate for the slower per-molecule absorption rate, delivering nicotine efficiently in small, low-power devices.
Aerosol vs. Cigarette Smoke
What comes out of a vape looks like smoke but is physically quite different. Cigarette smoke is produced by combustion, burning plant material at temperatures above 600°C. This creates solid particles, including soot (black carbon), tar, and thousands of chemical byproducts. Vape aerosol is produced at much lower temperatures without combustion. The particles are predominantly liquid-based droplets, smaller in size, and far more volatile, meaning they evaporate and dissipate in the air faster than cigarette smoke particles.
The concentration of particulate matter in vape aerosol is also much lower than in cigarette smoke. This doesn’t mean the aerosol is harmless. When coil temperatures rise above about 270°C, the production of harmful byproducts like formaldehyde increases sharply. One lab study found formaldehyde emissions jumped nearly sixfold when heating temperature increased from 270°C to 318°C. Keeping the wick saturated and the power setting reasonable helps keep operating temperatures in a range where fewer of these byproducts form.
Draw-Activated vs. Button-Fired
The simplest vapes are draw-activated. You inhale, the pressure sensor detects it, and the coil heats up automatically. There are no buttons, no menus, and no settings to configure. This is the standard design for disposable vapes and most beginner pod systems.
Button-fired devices require you to press and hold a power button while inhaling. This gives you more control over when the coil starts heating and for how long. More advanced devices add screens, wattage controls, and temperature limiting. Many modern vape batteries include built-in safety features: overcharge protection to prevent the battery from charging past its capacity, short-circuit protection that shuts the device off if a wiring fault is detected, and low-voltage protection that powers the device down when the battery is nearly depleted.
Mouth-to-Lung vs. Direct-to-Lung
Vapes are generally designed around one of two inhalation styles, and the hardware determines which one the device supports.
Mouth-to-lung (MTL) devices have a narrow mouthpiece and restricted airflow, similar to drawing on a cigarette. You pull vapor into your mouth first, then inhale it into your lungs in a second step. These devices run at lower power, use higher-nicotine liquid, and produce modest amounts of vapor. Most disposables and pod systems are MTL devices.
Direct-to-lung (DTL) devices have a wider mouthpiece and much more open airflow. You inhale the vapor straight into your lungs in one breath, like breathing through a straw. These devices run at higher power, use lower-nicotine liquid (typically 3 to 6 mg/mL), and produce significantly more vapor. DTL devices often include adjustable airflow rings so you can fine-tune the draw resistance to your preference.