This usage is specific to the Transport Regulations, and should otherwise be avoided. A solid object which is not itself radioactive but which has radioactive material distributed on its surfaces. SCOs shall be in one of two groups: (a) SCO-I: A solid object on which: (i) the non-fixed contamination on the accessible surface averaged over 300 cm2 (or the area of the surface if less than 300 cm2) does not exceed 4 Bq/cm2 for beta and gamma emitters and low toxicity alpha emitters, or 0.4 Bq/cm2 for all other alpha emitters; and (ii) the fixed contamination on the accessible surface averaged over 300 cm2 (or the area of the surface if less than 300 cm2) does not exceed 4 x 104 Bq/cm2 for beta and gamma emitters and low toxicity alpha emitters, or 4 x 103 Bq/cm2 for all other alpha emitters; and (iii) the non-fixed contamination plus the fixed contamination on the inaccessible surface averaged over 300 cm2 (or the area of the surface if less than 300 cm2) does not exceed 4 x 104 Bq/cm2 for beta and gamma emitters and low toxicity alpha emitters, or 4 x 103 Bq/cm2 for all other alpha emitters. (b) SCO-II: A solid object on which either the fixed or non-fixed contamination on the surface exceeds the applicable limits specified for SCO-I in (a) above and on which: (i) the non-fixed contamination on the accessible surface averaged over 300 cm2 (or the area of the surface if less than 300 cm2) does not exceed 400 Bq/cm2 for beta and gamma emitters and low toxicity alpha emitters, or 40 Bq/cm2 for all other alpha emitters; and (ii) the fixed contamination on the accessible surface, averaged over 300 cm2 (or the area of the surface if less than 300 cm2) does not exceed 8 x 105 Bq/cm2 for beta and gamma emitters and low toxicity alpha emitters, or 8 x 104 Bq/cm2 for all other alpha emitters; and (iii) the non-fixed contamination plus the fixed contamination on the inaccessible surface averaged over 300 cm2 (or the area of the surface if less than 300 cm2) does not exceed 8 x 105 Bq/cm2 for beta and gamma emitters and low toxicity alpha emitters, or 8 x 104 Bq/cm2 for all other alpha emitters