Decreases with altitude

Atmospheric Pressure

As altitude increases atmospheric pressure and oxygen concentration in the atmosphere decreases. A point is reached where humans cannot breath anymore.

Death zone
The death zone, in mountaineering, refers to altitudes above a certain point where the amount of oxygen is insufficient to sustain human life for an extended time span. This point is generally tagged as 8,000 m (26,000 ft, less than 356 millibars of atmospheric pressure).
Wikipedia, Effects of high altitude on humans, 2019

Humans cannot breath at high altitude. Above the death zone you have to bring your own oxygen. This was only known recently, however this was portrayed in the Quran 1400 years before it was discovered. The Quran says that as we ascend to the sky it becomes more difficult for us to breathe:

[Quran 6.125] Those whom Allah wants to guide, He opens their chests to Islam; And those whom He wants to leave astray, He makes their chests tight and constricted, as if they are ascending to the sky: Such is the penalty of Allah on those who refuse to believe.

"He makes their chests tight and constricted, as if they are ascending to the sky" this turned-out to be correct. No mistakes in the Quran.

How could an illiterate man who lived 1400 years ago have known how altitude affects breathing?  

Miracles Of Quran

The Quran (Koran, the book of Islam) contains scientific knowledge that could not have been known 1400 years ago. It ranges from basic arithmetics to the most advanced topics in astrophysics. You are invited to go through those miracles and judge for yourself.

STUDY OF THE EARTH

Geology

Coal, Landslide, Weathering - Erosion, Porous Rocks, Mass Extinction, Steam Explosions, Mountains, Internal Waves, Earth, Pumice, Photic Zone, Tectonics, Dead Sea, Sinkhole, Volcano, Shorelines, Minerals, Hydrothermal Vents, Freshwater, Fire Whirl, Rocks Crack, Subduction, Fault Lines, Earthquake, Soil Expansion, Flash Flood.

SCIENCE OF LIVING ORGANISMS

Biology

Fetal Development, Honey, Cholesterol, Meiosis, Antioxidants, Fats, Hypoxia, Miscarriage, Gardens, Photosynthesis, White Hair, Pollination, Lightning Strike, Inner Ear, Cataracts, Vision, Bones, Milk, Brain Functions, Evolution, Honey Bees, Human Senses, Frost, Gender, Eye Pupil, Womb, Fingerprints, Skin Nerves, Fasting, Breastfeeding, Eardrum, Fetus, Fluorescence, Human Embryo, Bedsores, Perspiration, Bacteria, Plant Stress.

SCIENCE OF Quantity, SPACE, AND CHANGE

Mathematics

Distance, Prime Numbers, Pi, Arithmetics, Relational Algebra, Base-19.

study of the past

History

Paper Money, Hieroglyphs, Digital Books, Calendar, Moses, Pharaoh's Mummy, Haman, Karnak Temple, Pharaoh, Flight, Noah, Dead Sea, Pompeii, North, Petra, Water Dam.

ANIMAL SCIENCE

Zoology

Raptors, Spider Web, Ants, Honey Bees, Colonies, Animal Languages, Mosquito, Crow, Nocturnal Animals, Housefly.

STUDY OF THE ATMOSPHERE

Meteorology

Sea Breeze, Orographic Effect, Wind, Volcanic Gases, Mass Extinction, Microburst, Cloud Seeding Dew, Shorelines, Fire Whirl, Freshwater, Atmospheric Pressure, Flash Flood, Weight Of Clouds.

SCIENCE OF CELESTIAL OBJECTS

Astronomy

Sunlight, Full Moon, Meteorites, Exoplanets, Planetary Orbits, Magnetosphere, Moonlight, Day, Multi-Star System, Iron, Starlight.

SCIENCE OF ELEMENTS AND COMPOUNDS

Chemistry

Viscosity, Superionic Water, Photosynthesis, Volcanic Gases, Mass Extinction, Bones, Steam Explosions, Internal Waves, Pyramids, Hydrogen, Water Stratification, Cloud Seeding, Fluorescence, Pompeii, Rust.

SCIENCE OF MOTION AND BEHAVIOR THROUGH SPACE AND TIME

Physics

Work, Light, Atoms, Pairs, Speed Of Light, String Theory, Rayleigh Scattering, Terminal Velocity, Time Relative, Wormholes, Pulsars, Gravity, Spacetime, Armor Peircing, Gravitational Waves, Sonic Weapons, Mass, String Theory, Equivalence Principle, Red Shifting.

SCIENCE OF THE ORIGIN AND EVOLUTION OF THE UNIVERSE

Cosmology

Shape Of Universe, Age Of Universe, Seven Heavens, Big Bang, Expanding Universe, Sound Waves, Isotropy, Primordial Smoke, Dark Energy, Galaxy Filaments. Dark Energy

Please link to

miracles-of-quran.com