30 CFR § 57.6303
Initiation preparation.
(a) Primers shall be made up only at the time of use and as close to the blast
site as conditions allow.
(b) Primers shall be prepared with the detonator contained securely and
completely within the explosive or contained securely and appropriately for
its design in the tunnel or cap well.
(c) When using detonating cord to initiate another explosive, a connection
shall be prepared with the detonating cord threaded through, attached securely
to, or otherwise in contact with the explosive.
[58 FR 69596, Dec. 30, 1993]