Your descriptions are great and I certainly feel the building tension. It might be interesting to see where you can take this.

The mysterious, dangerous fog, a horror classic. Nicely done here, working in the five senses smoothly and without it feeling forced. Great job on the challenge.

Chemical fog, it’s more than horror parlor tricks to increase suspense and provide a visual foreshadowing. Worry and fear and tension are conveyed very well through this foggy scene.

This is simply told and the shock is developed innocently with the girl’s sudden realization of the danger. That gum really sticks with me! My only critique is that you used ‘was’ too much.