OSHA's regulation does not set specific response time requirements for the term "near proximity," however, in areas where accidents resulting in suffocation, severe bleeding, or other life-threatening or permanently disabling injury or illness are likely, a three- to four-minute response time, from time of injury to time of administering first aid, is required.
In other circumstances - where a life-threatening or permanently disabling injury is an unlikely outcome of an accident - a longer response time, such as 15 minutes, is acceptable.