It appears as a disoriented, male humanoid with an opened torso and his head reared far back, with glowing, inflamed lungs and glowing orange tumors sprouting on its body and especially its throat, as well as glowing, orange eyes. It is a tall, spindly creature with an opposable ribcage, which opens vertically and can be used to attack. The rainbow coloration present on various parts of the creature's body strongly resembles an oil slick.
This monster is similar to the Lying Figure and Straightjacket from earlier entries, but instead of spraying the player with acid, it spews a noxious black gas. This gas continuously leaks from its mouth, and flecks of burning embers are also present in it.
Smog are difficult to deal with due to their danger at both long and short range and their high amount of stamina; however, the beast does lack in speed. They attack by spewing their black, gaseous breath at Alex Shepherd in order to both deal damage and attempt to stun him. Smogs make a labored breathing and almost gurgling sound when attacking, which hints at how Joshua Shepherd died. At close range, they can attack by swatting Alex with their open ribcages. The easiest way to deal with a Smog is to shoot when their lungs are exposed, typically before they are about to exhale their noxious breath.
As a whole, the Smog is best avoided. However, Smogs will relentlessly pursue Alex, so if this simply isn't possible, the maximum amount of distance that can be gained from one and a pistol are the safest route. Alternatively, if the player has a circular saw, they could simply charge their attack to instantly kill a Smog. Considering Smogs take a while to release their smoke attack, this may be the best approach to dealing with a Smog in close combat.
Smogs are best dealt with by some well-placed handgun shots upon the opening of the torso just as they are about to unleash their smoke attack. Two or three shots to the lungs should kill it. An experienced player may be able to deal with the Smog with a fire axe by slowly approaching until it makes a gurgling sound, then dodging forward and attacking to knock the Smog back, creating an opening for a heavy attack. The circular saw works in the same manner, shearing the lungs as they bulge out. They can also be killed with the combat knife or ceremonial dagger by stabbing them in the lungs; if the player is skilled enough, they can run up to it and strike it with a single non-charged strong attack as it is readying its smoke attack and retreat unharmed. Using this method, it is possible to defeat a Smog while taking little to no damage; it does, however, take some patience and artful dodging, so it is not recommended.
The black gaseous attacks may symbolize the black lung disease that would have been common in the coal mines that figure prominently in the game, or of coal fires that would have also been a hazard. Due to the game's military themes, it may be symbolic of the chemical mustard gas used in warfare such as World War I. The gas could also be a symbol of the smothering guilt that Alex suffers, being on crooked feet as well as being curled up while staggering. It may also represent the repressed burning anger contained in Alex's body that comes out as "fire", instead of his usual violent behavior.
The Smog can be further seen as a symbol of the burning, smothering guilt that Alex suffers; the Smog's sudden bloating and anger at Alex may be interpreted as a indirect reference to Joshua's death, as the boy drowned with Alex as witness. Like Asphyxia, the Smog manifestation has a set of hands covering his face, as if mourning or crying in intense despair, or as an action of pain. Some of the fingers cover the eyes, which might allude to Alex's own willful repression of the memory of his brother's death.
Both the animation and the sound emitted by the Smog serve as a distant evocation of Asphyxia, as it too tries to choke the player with gas. The creature's prominent lungs, an obvious weak spot for Alex to exploit, also point to how Nora Holloway and Alex's brother died, one at the hands of the Order, the other through water, but both of them through suffocation, hence the Smog's bloating.
The conspicuous ribs, dripping organs, and seemingly atrophied penis of the Smog may evoke the skinned animals in Adam Shepherd's hunting room, which hunt Alex Shepherd down in the form of Ferals, and by a same occasion, Adam's anger towards his son Alex.
- When Alex kills a Smog, its torso will release one final puff of toxic air due to gaseous build-up after what may span between only a few moments to approximately a minute.
- The Smog's introductory appearance, its manner of movements and overall design were greatly inspired by the Armless Man seen in the Silent Hill film.
- The Smog's black, burning body resembles the Grey Children of the Silent Hill film. This may have also been a source of inspiration.
- Defeating one Smog in the Xbox 360 version unlocks the achievement "Clear the Air".
- Smog's name is a word for air pollution, smog.