Have you ever been trapped in a room with

Burns. Remember that flares are hot.

Also, the smoke etc would hurt his eyes. Alot.

His throat, too. Flares make your throat burn. Depending on the direction they're fired, I have to wonder why nothing caught fire.

That metallic smell/taste from a fireworks show. Multiplied by, like, a million.

A lot of coughing, so difficulty speaking and shouting. Probably no vomiting, though.

Also, the flares come in a few different colors (red, white, green, etc.), so it might get pretty groovy in that room. Until the fire starts.

Does he fire off these flares accidentally? Because flare guns are single shot, meaning he'd have to work pretty hard to light off five by mistake.

And the light. he probably won't be able to see.

You're not going to get the effect you think you are.

Smoke is warm/hot and rises. Especially if you have air coming into the room, it will be cold. This is all basic science. So the smoke from the flares will rise to the ceiling of the cave. It will form layers, with the hottest and thickest on the ceiling, the coolest and thinnest on the floor. Unless there is a strong draft, this is how smoke always forms in an enclosed space.

In a fire, the ceiling can be 1200 degrees+ while the floor might only be 100 degrees. This is why fire fighters get down on the floor. Question is whether your character will figure this out.

My guess is with a six foot ceiling, ten by ten floor space, the top layer would be very hot, slowly descending in temperature to the floor. Standing, the air will probably be too thick to breathe, while the floor will be okay. While the flares are burning, the in draft will increase in volume, as the flares burn of O2 and needed an increased supply to continue to burn. Visibility would be best on the floor, and impossible on the ceiling.

The O2 in his blood would diminish and he would probably feel dizzy if he could stand. He'd probably be disoriented from the changes in visibility. Even fire fighters, who train a lot in this environment, have gotten lost in bathrooms. Your visual input can range from not being able to see your hand in front of your face from the smoke, to everything being obscured and sort of foggy.

Best of luck,

Jim Clark-Dawe

It takes two holes to make a vent. If the smoke is escaping out of one hole, then "fresh" air should be coming in through another.

Hammerklavier reminds me of an important point. Without ventilation (which requires an inflow and an outflow), the flares will quickly use up the available O2, then barely burn. This is why flames in mines change color, becoming redder and sootier as the O2 goes down. Not a good sign for the miners, or the canary they had with them.

All of this smoke on the ceiling can lead to a flashover if there is a sudden influx of O2.

Best of luck,

Jim Clark-Dawe