Читать книгу Patty's Industrial Hygiene, Physical and Biological Agents - Группа авторов - Страница 62

Surface contamination can be located with a sensitive detector, such as a thin end‐window G–M counter. After finding a contaminated area, a dose measuring instrument may be employed to measure the dose rate from the contamination. The main concerns about contamination are transmission of the contaminant into the body via inhalation or ingestion following tactile transfer to the skin, or transmission of the contaminant to other clean areas. To estimate the transmission hazard, a smear test is performed to determine whether the surface contamination is fixed or whether it is loose, and therefore transmissible. Smear tests may also be conducted in areas where high background radiation levels exist. A smear test consists of wiping the suspected area with a piece of specifically purposed filter paper, and then measuring the activity on the paper using an appropriate detector. The area to be smeared is determined by the extent of the contamination and the physical conditions under which the survey is made; an area of 100 cm² is usually smeared. It must be emphasized that a smear test is a qualitative test whose chief purpose is to allow an estimate to be made regarding the degree of transmissibility of the contaminant. If significant transmissible contamination is found, then prompt decontamination procedures are recommended.