A couple of things with occlusive dressings:
Keep the occlusive dressing just slightly larger than the wound. If the occlusive dressing is too large, you essentially create a secondary pleural space.
This wasn't mentioned in our class but makes perfect sense to me.
Check for exit wounds. If found, apply an occlusive dressing to any additional sites.
We covered this well, although the CERT first aid module did a better job of teaching us to assess the patient.
Try to apply and seal the occlusive dressing when the patient exhales.
We weren't taught this but it now seems obvious.
If possible transport with the injured side down, but monitor patient’s condition constantly.
This was covered.
If the patient complains of an increase in difficultly to breath, a decrease in the level of conscious and/or distension (enlargement/engorgement) of the jugular veins (large veins in the neck), you may have “burp” the occlusive dressing to relive trapped air and/or blood.
We were taught to use three sides of tape or a pre-made occlusive dressing, but this makes perfect sense to me.