Let me tell you a story about this comparatively less known scientist.

His name was Fritz Haber.

He was a German scientist who won the Nobel Prize for inventing a process called formation of ammonia from hydrogen and atmospheric nitrogen, under conditions of high temperature and pressure.

Before Fritz Haber, nobody actually knew how to produce ammonia in the lab. And why is it important?

Because, we need nitrogen to grow our food in the field.

The nitrogen you have in the protein in your body or as we call it the building blocks of your body right now, probably came from the process that was discovered by Fritz Haber.

But Haber was a patriot. so during the WW 1 he was appointed by the German authority to develop poisonous gases those were used in trench warfare.

A scientist turned into a killer who actually is responsible for developing a process to feed the entire population of the world today.

The poisonous gasses those were developed by Dr. Haber and his team were so deadly that they would kill thousands of soldiers in a matter of seconds to minutes.

These poisonous gases would attack the lungs of the victim and irritate the respiratory epithelium so much that the lungs would try to compensate this irritation by secreting fluid into the alveolar space.

That would result in excruciating death of the soldiers due to respiratory failure as because the lungs would fill up with water in a very short period of time.

We call this process pulmonary edema.

I am going to explain how this happens. But before we go into further discussion let us look at the lung anatomy first.

Human respiratory tract starts from the nose and it ends with the alveolus those which are tiny air sacs found at the very end of the lungs’ airways.

At the end of the naso-pharynx trachea starts.

Which gradually branches into bronchi.

Like the branches of a tree but upside down.

The trachea divides into the right and left bronchi and enters into the hilum of the lungs.

From there they continue to branch off until they reach to the end.

At the end, they transform into alveoli.

These alveoli are very tiny air sacs.

They function as a container for air.

From these containers red blood cells absorb oxygen.

And before leaving the alveoli they also dump the carbon di oxide into them.

So that it can be released into the air.

This exchange of gasses occurs through the alveolar membrane that is about couple of micrometers thick.

We have on average 480 millions of alveoli in our lungs combined.

Where smaller lungs contain less than that and larger ones more.

If we would spread all the Alveoli and put them side by side it would take up an entire tennis court.

Such a huge surface area that has been crammed into such a small space in the body.

And all that effort is to ensure a proper ventilation.

Everyday when we go out we deal with many toxic air pollutants those directly come into the contact of the alveoli.

and as a result this sophisticated biological structures get damaged.

But, our lungs have the ability to fend of these toxic substances to some extent.

So we don’t die immediately.

It is like a silent war between the environment and the lungs.

Where the lungs are at constant struggle to maintain body's homeostasis.

Dr. Fritz Haber was researching for a gas that would absolutely overcome resistance of the lungs to obnoxious air particulates.

And Finally, he found one.

It was the chlorine gas.

This gas is so deadly that even a miniscule amount

if enters into the respiratory tract would completely annihilate the respiratory epithelium and people would die.

Let me explain how this happens.

If you looked at lung alveoli you should see this.

Please notice the tiny blood vessels those are entangled around the alveolus. We call them alveolar capillaries.

They're not actually separated from the alveolar wall rather they’re embedded into the alveolar wall.

In fact lung alveoli and capillaries share a same wall between them.

When a toxic gas enters into the alveolar space it reacts with the alveolar wall and as a result the alveolar wall gets damaged.

This creates tiny pores within the alveolar wall and the fluid content of the blood, which is predominantly water, starts to pour into the alveolar space.

Slowly, the whole lung tissue drowns into the leaking fluid.

This fluid in the alveolar space prevents entry of air into the lungs just like the way it would happen if you would drown in water.