Abstract: Security unit, particularly for storing payments in a retail outlet, comprising a secure, lockable housing with an inlet, a gas feed mechanism for conveying items introduced into the housing, and a removable package for receiving and storing payments. Before the package can be removed, the package is sealed in a tamper evident manner. The package is preferably a plastics container having a neck portion extending from its inlet, and gas outlets remote from the inlet through which gas introduced into the inlet is vented. The feed mechanism preferably comprises a channel through which payments are conveyed and gas inlets provided on opposed sides of the channel, inclined at an angle to that in which the items are conveyed. Gas is jetted through the channels to produce a gas flow which entrains an item to convey this through the channel.