... when is it safe to use one? And how should it be used?

Before use
Before using a stepladder, check that you are fit to be working at height. Then check both the condition and the position of the ladder.
A stepladder in good condition has:
- Feet firmly attached
- Clean treads
- Secure locking devices
- Secure fastenings when it is extended
A stepladder in a good position:
- Is fully open
- Is locked into place
- Will not move at the bottom.
- Stands on a surface that is:
- firm
- level
- clear
- dry
- not slippery
In use
- Only work on a stepladder for a maximum of 15 - 30 minutes at a time
- Only carry light materials and tools (up to 10 kg)
- Do not overreach
- Keep both feet on the same rung or step throughout the task
- Make sure you have a safe handhold available on the steps
- Avoid side-on working
Is a ladder right for the job?
If you are not sure that it is right to use a ladder speak to your supervisor or your OHS representative.
Further reading
NSW WorkCover has a useful Safety Guide Portable Ladders which provides advice on the safe use of all types of ladders, and includes references to relevant Australian Standards. Another useful publication is Working off stepladders [pdf]
From the UK's HSE:
- INDG402 - Safe use of ladders and stepladders
[PDF 318kb]
This guidance helps employers, the self-employed and people who work from ladders:- know when to use a ladder
- decide how select the right sort of ladder for the job;
- understand how to use it
- know how to look after it
- take sensible safety precautions.
- INDG405 - Top tips on ladder and stepladder safety
[PDF 38kb]
Useful information on safe ladder use in a handy pocket size.
Taken from information on the UK HSE website.