Schwoz' special gas mask seems to light up at its tip when he talks, but it doesn't always work that way, often lighting up when anyone talks.
No contaminated person can go outside for fear of contaminating the citizens of Swellview - but Henry, Ray and Charlotte have already been outside, yet no inquiry was made into whom they might have met. Since Charlotte had come from home, she might have infected her family as did Henry, but no investigation was made.
An adult human body contains 1.2-1.5 gallons of blood, yet Schwoz removes three gallons of Jasper's blood, squeezing out a few last drops without killing him.