Instruments or equipment switches, range selection knobs, other function activation switches. When taking a smear the surveyor applies moderate pressure with one or two fingers on the back of the smear medium and rubs it over the surface to be surveyed. Some like to use a No. 8 or 10 rubber stopper to backup their smears. The area per smear should be usually limited to about 100 square cm or 16 square inches. In evaluating the results of an area survey the surveyor must keep one fact in mind.
Contamination is like an iceberg.
Depending on the levels of contamination detected, a more extensive survey may be required immediately and an evaluation of possible personnel exposure, or contamination spread undertaken at once.