In short
The main duties on employers in the Health and Safety at Work etc. Act 1974 are qualified by the words "so far as is reasonably practicable". It means weighing a risk against the money, time and trouble needed to control it. You must take a precaution unless its cost is grossly out of proportion to the risk. If you are prosecuted, section 40 of the Act puts the burden on you to prove you could not reasonably have done more.
Example
a half-day job
Sam runs a two-person roofing business. A customer wants slipped tiles replaced above a conservatory. It is a half-day job with a small margin, so Sam's first thought is to work from a ladder. His apprentice, Leah, asks what happens if one of them falls through the conservatory roof. Sam weighs it up. A fall through the glass could cause serious injury. Hiring a tower scaffold adds some cost and an hour on site. That is nowhere near grossly out of proportion to the risk, so it is reasonably practicable. Sam builds it into his price.
An illustrative example, not a real case.
What the law says
- Sections 2 and 3 of the Health and Safety at Work etc. Act 1974 require employers to protect workers and others "so far as is reasonably practicable".
- The courts have said this is narrower than "physically possible". You weigh the risk against the sacrifice needed to avoid it, in money, time or trouble.
- A measure can only be left out if the sacrifice is grossly disproportionate to the risk. The scales are tilted towards safety.
- Section 40: in a prosecution, the defendant must prove it was not reasonably practicable to do more than was done.
How to weigh it up
- 01
Size the risk
Think about how likely harm is and how serious it could be, for workers, other trades and the public.
- 02
Start from good practice
Check HSE guidance, Approved Codes of Practice and industry guidance for the work.
- 03
Look at the options
Ask first whether you can remove the hazard, and treat protective equipment as the last resort.
- 04
Decide and record
Adopt every measure that is not grossly disproportionate, and note why you ruled anything out.
Good practice is your benchmark
For most everyday risks you do not need to work out the balance from scratch. HSE says that if you follow its guidance you will normally be doing enough to comply with the law. Approved Codes of Practice have a special status: if you are prosecuted and did not follow one, you will need to show you complied in another way. Do not assume your controls are adequate just because nobody has been hurt yet. Good advice matters most where the work is unusual, the guidance does not quite fit, or there is pressure to cut a corner.
What the courts have said
Edwards v National Coal Board [1949] 1 KB 704
The Court of Appeal said "reasonably practicable" is narrower than "physically possible". The risk is weighed against the sacrifice needed to avert it, and a precaution can only be left out if the sacrifice is grossly disproportionate. The courts still treat this as the classic statement of the test.
R v Chargot Ltd [2008] UKHL 73
The House of Lords said sections 2 and 3 set a result the employer must achieve. Once the prosecution shows it was not achieved, the employer must prove it did all that was reasonably practicable. The law is concerned with material risks, not trivial or fanciful ones.
Common questions
What is the difference between SFAIRP and ALARP?
SFAIRP means "so far as is reasonably practicable" and is the phrase used in the law. ALARP means "as low as reasonably practicable" and is widely used in industry. Both come down to the same test: weighing the risk against the money, time and trouble needed to control it.
Can I just choose the cheapest option?
No. Under the Act you must take a precaution unless its cost is grossly out of proportion to the risk. For most everyday risks, following HSE guidance will normally be enough.
Do I have to eliminate every risk?
No. HSE says you are not expected to eliminate all risks, but you do need to do everything reasonably practicable to protect people.
Who has to prove what was reasonably practicable?
In a prosecution, the defendant does. Section 40 of the Act puts the burden on you to prove you could not reasonably have done more.
How NXT-HSE can help
NXT-HSE can review your controls against recognised good practice and help you decide, and record, what is reasonably practicable. The decisions and the legal duties stay with your business.
Sources
- Health and Safety at Work etc. Act 1974, section 2
- Health and Safety at Work etc. Act 1974, section 40
- HSE: introduction to managing health and safety, the law
- HSE: legal status of HSE guidance and ACOPs
- HSE: steps needed to manage risk
- UK Supreme Court: Baker v Quantum Clothing Group [2011] UKSC 17
Sources checked 27 September 2026 against current Health and Safety Executive guidance and legislation. This guide is general information, not legal advice; your legal duties stay with your business.