There is no gear-related reason why one would black out if they were scuba diving with an open-circuit system (i.e., compressed air) provided that the gas mix they are breathing is appropriate for the depth. Breathing the wrong gas mix for the depth can cause blackout or seizures. If you are diving recreationally and within your limits with a standard gas (e.g., air, EAN 32, etc) you should be fine.
There have been a few cases where scuba divers have died while diving closed-circuit systems (i.e., rebreathers) in which case the incident was death by drowning following passing out because of equipment malfunction - in most cases the CO2 was being scrubbed, but there was insufficient oxygen being injected into the circuit leading to a blackout.