OSHA does not require employers to have a certain number of kits in the workplace. This should be based on several factors including the size of the workplace, number of employees, likelihood and location of possible accidents, etc. Also, 1910.151(a) states that the employer must have a medical professional to advise on matters of plant health, such as what first aid supplies should be available, the amount of supplies needed, and where those supplies should be placed. In other words, OSHA would expect employers to consult their medical professional for guidance.
In addition, employers may also discuss this issue with a local ambulance service or outside emergency responders for suggestions. First aid supply vendors might also be able to provide specific recommendation for a workplace.