The size and nature of the workplace dictates the size of its first aid kit. A workplace with heavy machinery will require different first aid supplies than an office setting. Security personnel may know the location of a first aid kit and be trained in first aid. There are usually legal regulations for the standard contents of a first aid kit required in different situations (for example, in the US those set by the Occupational Safety and Health Administration and in the UK set by the Health and Safety Executive). The host of any large gathering of people is responsible for responding to any potential medical emergency. This includes making sure that a responsible person has ready access to a first aid. Schools keep a first aid kit in the main office, whether or not there is a designated nurse. Coaches and other athletic trainers should keep a first aid kit handy during sporting events. Soldiers carry a rudimentary first aid kit attached to their belt or harness.
It often contains a field dressing and powders or ointments to stop bleeding or prevent infection. It is a military rule that you always use the injured person's first aid kit, not your own, to tend to their injuries. You may need yours later. Lifeguards must have quick access to a well-stocked first aid kit at their place of employment. In Canada, they are trained to the level of "Standard First Aid," and can deal with many first aid situations from a stubbed toe to a victim with C-spine injuries and absent vital signs. Obviously, lifeguards are no replacement for a paramedic or doctor, but if you require care and a lifeguard is nearby, remember that they have training and a duty to act. Generally speaking, you may not use their first aid kit; they will have to provide care, and write a report per the regulations in your geographical area and the workplace.