Segregation must be done in two steps. For regular quantity DG, follow 18.104.22.168 (a) where segregation must be made to avoid chemical reaction. You need sufficient knowledge of chemistry to apply this method. For instance, Class 8 with a high alkali nature and Class 8 with a high acid nature cannot go together. If mixed you will have an explosion. The manufacturer or the shipper would have technical knowledge so we will need to rely on them. Secondly, you segregate per 22.214.171.124 (b) or Table 9.3.A which any layman can apply. Note that at the intersection of Class 8 and Class 8, there is no “X” but it requires segregation per 126.96.36.199 (a).
For LQ DG, the process is the same. Firstly, segregate per chemical knowledge following 188.8.131.52 (a), and, secondly, segregate per 184.108.40.206 (b) or Table 9.3.A.
For Overpacks, segregation must be made following the same process. Refer to the first two and a half lines of 220.127.116.11.1 where segregation must be done first by applying chemical knowledge. Thence apply the remaining part of 18.104.22.168.1 by segregating per Table 9.3.A.
Finally, for EQ DG, see 2.6.1 Applicability. In the 4th bullet point, you will see that segregation per 22.214.171.124 (a) is a “must”, whereas segregation by 126.96.36.199 (b) or Table 9.3.A is not mentioned, therefore exempted.