The second character in the code is a letter selected from the range P, R, S, T, W, X, Y, Z which indicates the type of personal protection to be worn, the possibility of violent reaction, and whether the substances and the medium employed should be contained or the substances diluted. The characters are generally black on a white background. Personal Protection The letters P, R, W or X indicate that a full chemical protection suit and breathing apparatus should be worn. The letters S T Y and Z may on occasion appear. These reversed characters indicate that breathing apparatus need only be worn if the substances are involved in a fire. Frequently in text these appear in a box, ie. S T Y or Z to indicate that they are to read as a white letter on a black background. Contain or Dilute The letters P, R, S and T indicate dilution while W, X, Y and Z indicate containment. Both seek to reduce the hazard or prevent escalation of the incident. 'Contain' attem...
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