Are Indoor dryer vents safe?

Safe is a relative word. Crossing the street can be safe, depending on whether or not a car is coming. Likewise, venting a dryer indoors will increase moisture levels as well as introduce dust/lint into the air- which can't be benficial to a child with asthma. However, venting indoors will not kill you immediately. Like anything, repeated exposure could cause potential health hazards and mold in your home.