What Is an E-Cigarette and How Does It Work?

An e-cigarette is a small battery, a heating coil, and a reservoir of flavoured liquid. Press the button or inhale, the coil heats the liquid to a few hundred degrees, and the liquid becomes an aerosol you breathe in. Nothing is set on fire, which is the single most important difference between this and a cigarette.

Everything else about it, including how much nicotine you end up taking in, depends on details that most people never look at once.

What is inside an e-cigarette?

Strip any device down and you find five parts:

• The battery. Almost always lithium-ion. In a disposable it is sealed in; in a refillable device it is either built in or a removable cell.
• The coil, also called the atomiser. A thin wire that heats up when current runs through it, usually to somewhere between 200 and 300 degrees Celsius.
• The wick. Cotton, or occasionally ceramic, sitting against the coil. It draws liquid in so the coil always has something to heat.
• The e-liquid. Propylene glycol and vegetable glycerine as the base, plus nicotine and flavourings. That is the whole recipe in most products.
• The sensor and mouthpiece. Older devices had a fire button. Most modern ones use an airflow sensor that fires the coil the moment you draw on it, which is part of why puffing becomes automatic.

There is no combustion anywhere in that chain. The liquid is heated until it evaporates and then immediately condenses in the cooler air of the mouthpiece into microscopic droplets.

Why aerosol is not the same as vapour

This distinction sounds pedantic and is not.

Vapour is a substance in gas form, like steam. What leaves a vape is an aerosol: a suspension of extremely fine liquid particles in air. Those particles are the delivery vehicle. They carry nicotine deep into the lungs, along with the flavour chemicals, the glycol base, and small amounts of metals shed by the coil, such as nickel and chromium.

The “it’s just water vapour” line survives because the cloud looks like steam and mostly disappears. It is worth retiring. An aerosol is substantially less harmful than smoke, because smoke is a burning-plant aerosol carrying tar, carbon monoxide and roughly 70 known carcinogens (CDC). But less harmful is a comparison, not a clean bill of health.

The four generations of e-cigarette

Generation	Typical form	Nicotine style	What changed
First	Cigarette-shaped “cigalike”	Low-strength freebase	Looked like a cigarette, delivered little nicotine
Second	Pen-shaped, refillable tank	Freebase, 3-18 mg/ml	Longer battery life, user-filled liquid
Third	Box mods, adjustable power	Low strength, big clouds	Enthusiast era, high vapour, harsh at high nicotine
Fourth	Pods and disposables	Nicotine salts, high strength	Smooth high-dose inhale, pocket-sized, always ready

The fourth generation is the one that changed public health, and the reason is chemistry rather than design. Freebase nicotine at high concentration is harsh; your throat stops you before your bloodstream is satisfied. Nicotine salts add an acid that lowers the pH, so a very high concentration goes down smoothly.

That removed the natural brake. A cigarette ends after seven minutes because it burns out. A pod does not end. It sits charged in your pocket and gives you a smooth hit every time you reach for it, which is why real-world use is often three or four hundred small puffs a day rather than twenty distinct events.

How much nicotine are you actually getting?

There is no clean answer, and that is the point worth taking away.

Liquid strength is capped at 20 mg/ml in the EU and UK. In markets without that cap, 50 mg/ml salts are standard in pods and disposables. On top of strength, delivery depends on coil resistance, device power, how long each draw lasts, and how deeply you inhale.

Two people can use the same 600-puff disposable and absorb amounts that differ by a factor of three. Which means the only figure that describes your intake is your own puff count, and almost nobody knows theirs. Ask someone who vapes daily how many puffs they took yesterday and you will get a guess that is usually low by half.

What about the health side?

Briefly, because it deserves its own reading rather than a paragraph:

• No combustion means no tar and no carbon monoxide, which is why health bodies including the NHS assess nicotine vaping as substantially less harmful than smoking.
• Long-term data does not exist yet. The product category is under twenty years old. “Not proven harmful” and “proven safe” are different sentences.
• Nicotine itself is a stimulant that raises heart rate and blood pressure, and there is real concern about exposure during adolescence, when the brain is still developing (Truth Initiative).
• Flavour chemicals are food-grade, which tells you they are safe to swallow, not safe to inhale. Those are separate tests.

If you are reading this because you want to stop

Then the useful part of understanding the device is understanding the trap in it: there is no built-in endpoint. Cigarettes are self-limiting and vapes are not, so intake drifts upward quietly, and the day you decide to quit you are working from a number you have never measured.

Start by measuring it. For the next three days, count every puff and change nothing else. No cutting down, no guilt, no target. You are just collecting the number, and the number is almost always a surprise. Once you have a real baseline, reducing it by ten to twenty percent a week is arithmetic rather than willpower.

Puff Counter exists for exactly that: it counts the puffs you take without noticing and rebuilds each week’s limit from your own average, so the step down is always small enough to make.

Two minutes, starting now: open the notes app on your phone and add a tally mark for every puff you take today. That is the whole first step, and it is the one that makes every later step possible.