A missed approach is executed when the pilot or ATC feels that a safe landing cannot be accomplished. They can be initiated by either the pilot or ATC.
During a missed approach, the AIR controller may issue heading instructions to aircraft who may be in confliction (i.e. departure just ahead of a missed approach).
As soon as possible after a missed approach is initiated, the AIR controller should contact the Approach controller to inform them of the missed approach. The approach controller will then tell AIR how they would like the aircraft. They may like it to follow the standard missed approach procedure, or may issue a tactical heading and/or altitude to give the missed approach minimal delay. If for whatever reason, you are not able to coordinate fast enough with the approach controller, the aircraft should be instructed to carry out the standard missed approach procedure.
When a missed approach is carried out, free flow on departures is automatically suspended. The AIR controller must request a release from radar for the next departure and/or request that free flow can resume.