In low-hazard environments (as indicated by your risk assessment) for example offices, shops and libraries, the number of first aid personnel required in the workplace is dependent on the number of employees.
If you have fewer than 25 employees, you are required to have at least 1 appointed person to be in charge of any first aid.
If you have between 25 and 50 employees, you will need at least 1 Emergency First Aid at Work trained first aider.
If you have more than 50 employees there has to be at least 1 First Aid at Work trained first-aider for every 100 employees.
Things to think about:
Can any injuries or illness that may occur be dealt with by the first aiders you provide?
Where first aiders are necessary, is there still possibility of an accident or sudden illness? This may mean you wish to consider providing qualified first aiders.