You bring the cigarette to your lips and inhale. Within seconds, billions of molecules invade your body and brain. The cigarette is one of the fastest delivery systems known — quicker than an intravenous shot. Here is the precise timeline of what happens, puff by puff.

The inhalation: an aerosol of chemistry

When you light up, combustion at the burning tip reaches 800 to 950 °C. In that hot zone, tobacco and its additives thermally break down into more than 7,000 substances: gases, vapours, ultrafine particles.

You inhale that aerosol down through your airways:

• The smoke crosses the mouth (where some of the nicotine is already absorbed by the mucous membranes).

• It travels down the trachea and bronchi.

• It reaches the alveoli — a sea of 300 million tiny sacs where blood swaps gases with the air.

0 to 7 seconds: the wild ride to the brain

1. 0 s you inhale.
2. 2-3 s smoke reaches the alveoli, nicotine crosses the alveolar-capillary barrier into the blood.
3. 3-5 s nicotine-rich blood travels back to the left side of the heart.
4. 5-7 s nicotine reaches the brain, crosses the blood-brain barrier, and locks onto the nicotinic acetylcholine receptors.

That speed is the key to the cigarette's powerful addiction. The faster nicotine reaches the brain, the more strongly the brain pairs the gesture (smoking) with the reward (dopamine). That is why patches and gums (slow absorption) are far less addictive than a cigarette.

7 to 30 seconds: the nervous system fires up

Once locked into the brain, nicotine triggers a cascade:

In the bloodstream, this is also the moment of vasoconstriction: small vessels tighten, the skin pales, the extremities cool slightly.

30 seconds to 3 minutes: peak and plateau

Your heart beats 10 to 20 more times per minute. Blood pressure can rise by 5 to 10 mmHg. That cardiovascular workload lasts about 30 minutes.

While you smoke: what creeps in silently

While nicotine is throwing its party in your brain, the other components do their toxic work:

• Carbon monoxide (CO) locks onto your haemoglobin, taking the place of oxygen. Your tissues are poorly oxygenated.

• Tar deposits on the bronchial walls.

• Acrolein and hydrogen cyanide paralyse the cilia that clean your airways.

• Fine particles trigger local inflammation.

30-60 minutes later: the peak fades, withdrawal begins

Nicotine has a short half-life in the blood (about 2 hours), but its brain effects fade faster: the sense of well-being starts to slip after 30-60 minutes. That is when your brain starts demanding the next cigarette.

For someone smoking a pack a day, the cycle repeats 20 times across 16 waking hours — roughly every 50 minutes.

8 hours later, if you have not lit up again

1. 8 hours carbon monoxide is cleared from the blood. Oxygenation returns to normal.
2. 24 hours cardiovascular risk starts dropping.
3. 48-72 hours nicotine has fully left the body, withdrawal peaks.
4. 2-3 weeks nicotinic receptors start returning to baseline.

That is what happens if you stop. Light another cigarette and the cycle restarts.

And vaping?

With a vape, absorption is generally slower (10-30 seconds to reach the brain, not 7), because the liquid's pH is more acidic and nicotine binds more slowly. That is also why vaping is less addictive at equivalent dose — and why many vapers gradually lower their nicotine strength.

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