You can stumble upon these areas that are filled with a red mist in Redfall. This dead mist can cover entire streets and can literally cost you your life because standing in the red mist will slow you down and you will take damage from it. You can take an alternative route to your next objective, however, sometimes you just need to be in that area and there is a way to clear the red mist.
The red mist in Redfall occurs when a Bloodbag gets petrified. Bloodbags are half-transformed humans that act as cows for the Vampires to feed on. All the excess blood that gets stored in their body slowly gets released when they are petrified.
What you want to do is scout the area for any half-petrified Bloodbags. You want to fully transform them into stone by using a UV Light. This stops them from emitting any new Death Mist and you can shatter them by punching them in the face. You have about 10 seconds to shatter the vampire or else the Red Mist will return. By removing the source of the red mist, you prevent it from spreading further and clear out the area itself.
Pro Tip: Aim down sights with your UV weapon to create a focused beam. That way you are much quicker at achieving your goal.
Hopefully, this and my other Redfall guides will help you on your way!