#the gray

Which also finally explains to me how the show decided to depict the Grey in the Kiramann family's archives:

A personification of the gas, depicting it as a monster that poisons the people of Zaun (or those who breathe in it at least) with round glowing eyes and a black body, and who this image reminds you of? (at least to me)

Kindred!

More specifically Wolf

and what does the "Wolf" represents

Wolf:

Wolf is the bestial half of the Kindred, representing a violent death. Those who will not fall to Lamb's arrows doom themselves to Wolf's jaws as he goes on the chase. Always hungry, he feels emotion but does not truly understand it - the counterpart to Lamb's impassive knowledge of feelings. The Kindred stalk the world, bringing peaceful death to those who will fall by Lamb. All who do not make one more chase for Wolf.

a violent death: because obviously no one, be it in Zaun or elsewhere, would like breathing in poisonous gas that slowly kills you so they do what they can to escape it (like Viktor, who is chocking on his own blood as it has already infected/ruined/damaged his lungs, eating his insides slowly over the years and decided to leave the toxic air of Zaun sometime before the Kiramann family ask their architects to build the ventilation system, which means he was at least affected until his late teens. [timeline under])

Which is funny if you think a Wolf [Ambessa] manipulated the Pilties in using this very toxic gas against a terrified population (borders closed, more enforcer brutality) for the actions of one girl.

Council Bombing -> Ambessa helps Renni attack the funerals -> Successfully makes Caitlyn declare Martial Law -> Caitlyn uses the Grey -> Jinx sends it back up.

--- IGNORE THIS IF THE TIMELINE DOESN'T INTEREST YOU

Timeline from what I can understand based from the show and some of the wiki (using this timeline for help):

APF = After Piltover Foundation

168 APF: Viktor is born.

177-187 APF: Vander, Silco, and Felicia work for the "Nation of Zaun" (discuss revolutionary ideas). During this period, they possibly negotiated for better working conditions in the mines and measures to keep The Grey at bay.

178 APF: Vi is born.

182 APF: Pow-Pow is born.

177-180 APF: Viktor works with Singed (between ages 9-12, though his exact age during this period is unclear).

185-187 APF: wiki -> "Still, somewhere in his late teens, Heimerdinger encounters him and takes him under his wing, allowing him to study at the University of Piltover. Viktor goes on to become his assistant as Dean of the Academy." "Late teens" usually means 17-19, so Viktor likely left Zaun at this time.

193 APF: Welcome to the Playground takes place.

--- END

BUT going back to the Grey and Kindred:

This "violent death" is also shown when Silco (S1EP7) is seen using what can be assumed as a small (approx. same size of a fire extinguisher) container with the Grey to threaten the Chem-Barons. We can see the plants quickly wither away during Silco's speech.

(Obviously ignore the way Finn is violently chocking and spasming after breathing in the Grey for less than a minute.)

If the episode follows real-time pacing, approximately 117 seconds pass during this scene:

15:44 [we can hear the hissing sound of Sevika opening the container]

17:41 [Sevika starts the ventilation system and opens the door])

So around 1 minute and 57 seconds for the very big plants to die.

Silco's speech: "What's that? Oh, you don't recognize it? Have you forgotten where we came from? The mines they had us in? Air so thick it clogged your throat. Stuck in your eyes. But I pulled you all up from the depths. Offered you a taste of topside. And fresh air. I gave you life. Purpose. But you've grown fat and complacent. Too much time in the sun. We came from a world where there was never enough to go around, Finn. That is why we fight. Do you remember?  […]  Don't forget again."

[Side-by-side comparison to better see the damage]

In this scene, we can see the sky through the fan’s window—clear blue sky, clouds—meaning there’s open air and wind. Once the doors and windows are opened, the gas can escape.

But what happens when it’s released below? In the Lanes, where Jinx is?

There are no doors to open, no windows to break. The gas stays and doesn’t dissipate. (Unlike where Jinx sent it, which was an open street where it quickly dispersed.) It accumulates.

And in a population mostly consisting of sick, starving, and (or) drugged people, many with preexisting illnesses, it doesn’t take much to go from “it just stings my eyes and hurts my throat” (enforcers) to “I’m already sick, and this is making it worse.”

Which also shows in the Kiramann's archives what a prolonged exposure can do:

Extensive lung damage and damage to the respiratory system including nasal cavities.

If we compare it to smoke inhalation (which should be more or less the same toxicity than the Grey in my opinion [maybe more dunno]) from the msd manual:

Local irritant phenomena: Cough, wheezing, stridor (Stridor is an abnormal, high-pitched respiratory sound produced by irregular airflow in a narrowed airway during the inspiration phase)

Hypoxic manifestations: Confusion, lethargy, coma, tachycardia (a heart rate over 100 beats a minute), tachypnea (rapid breathing)

Upper airway injury usually causes symptoms within minutes but occasionally over several hours; upper airway edema may cause stridor. Significant orofacial burns can cause edema that significantly compounds the upper airway problems created by smoke inhalation.

Lower airway injury may also occur with upper airway injury and usually causes delayed symptoms (eg, oxygenation problems highlighted by increasing oxygen requirements or decreases in lung compliance after 24 hours or later).

Then there's the mini game Jinx Fixes Everything:

So does releasing The Grey into the streets of Zaun really not affect the common people? The ones who aren’t criminals, just trying to survive? Are the children working for the Chem-Barons affected?

[Zaunites praying to a mural of Janna, Jinx mentions that there are many stories telling how a "wispy wind woman" would rescue trapped miners underground]

Which brings me to the (leaked?) video of Zaunites entering Ekko and the Firelights' hideout—the one where the show removed the coughing in the final version.

Why?

Like, you spent all this time showing us —Viktor’s illness, Silco’s speech, the plants dying, a literal depiction of Runeterra’s Grim Reaper (at least in my opinion)—only to downplay the Enforcer SWAT team’s actions in the end? While at the same time putting extra emphasis on the harm done to the Piltover children?