WHS regulation 42 (3)
To meet your duty as a person conducting a business or undertaking (PCBU) to provide access to first aid equipment, facilities and trained first aiders you must have regard to all relevant matters, including the following: − the nature of the work being carried out at the workplace − the nature of the hazards at the workplace − the size and location of the workplace, and − the number and composition of the workers and other persons at the workplace.
Appendix C summarises the requirements for first aid kits, first aiders and first aid rooms.
Source: https://www.safeworkaustralia.gov.au/