Merrill Dunes has operated for 20+ years and despite thousands of players using the facility each year, the number of injuries has been amazingly low. As far as we know there has only been one eye injury, the issue you would expect to be the major risk. We have seen some really close calls, but those could be counted on one hand and were due to unusually foolish action on the part of the players involved. The one significant injury was a younger player, it was an unfortunate situation, and thankfully, as far as we are aware, the damage was not major.
The main issue we have seen is ankle injuries simply associated with running on normally uneven ground. Our "deflected momentum" game style may be a factor because players know that a hit isn't the end of the game - you simply run back to reactivation and keep going. At "hit and you sit" style fields, there is less running and more cautious sneaking, and a lot more sitting. Also most fields do not turn players loose in 7 acres of Action Zone! The rotating "postage stamp" system used on revenue flow operations means there isn't much room to run in!
One thing we learned early on is the futility of expecting refs to assist the safety cause. The idea of having lots of refs seems to have a bit of logic to it but there are glitches. The ref simply can't be everywhere like some sort of guardian angel. It is so rare that good quality masks on carefully prepped players ever come up in the field that no ref can stay on mental alert watching for the rare occurance. And paintball fields do not pay refs high wages. The refs are usually there because they are paintball enthusiasts. They need some indicator that they are a ref. Thus a sweater or some type of uniform. And as soon as you get someone in a uniform they automatically start giving orders and bossing people around. And that creates friction and minds slip off common sense safety. Low pay is offset by feeling important, but client alienation is a result.
The biggest safety feature that any paintball field should have is the capacity to use double lense / thermal masks. The reason players lift masks is primarily because they can't see due to lense fog. Thermals require anti fog spray at each cleaning as well, if it is really cold outside. Failure to use Thermals in cold weather or as evening approaches is a safety disaster waiting to happen.
The route to safety at a paintball field is maintained and servicing thermal masks - effective safety briefing at the start of play - civil relations between field staff and clients (you do not want a nickle plated mini dictator bossing them around) - constant positive contact with clients with a constant leaning on them to use their barrel plugs and keep those masks on - and wise layout of barrel plug baskets and general flow patterns. Having a field free of pallet nails and spinters and other safety hazards of course is standard practice.
If the group that is playing is getting along well together and is integrated effectively, in effect you have as many minds thinking about individual as well as group safety. Our Private Group policy is a huge factor in delivering this organic safety environment.
Safety cannot be decreed by a field. Safety is an attitude that needs to be carefully fostered by gentle and skilled human relation tactics. Some technical savy is also needed. Post holes and pallet forts tend to overcome good intentions! But human relation, not a gestapo system, is the answer!
Here is the #1 paintball or airsoft safety issue. If you ignor the importance of thermal masks in order to save some expense you had better hire lots of baby sitters to shadow players (and perhaps lead them to safety when they get so fogged that they can't see where they are going!) Fog control is a major issue.