24 is the least common denominator
We have to use Pythagorean theorem that says :

The missing length of the triangle is : 36 feet
Reason number 1 (before) is that you could contaminate your samples if you have foreign material on your hands.
Reason number 2 (after) is that you could spread<span>/or ingest dangerous chemicals or substances that you have handled in the lab.</span>
The distance of points P and B is 5