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Kerem IsmailHSE suggests at least one first aider trained in first aid at work (FAW) per 100 employees in low-hazard work, or per 50 in higher-hazard work such as construction, above 50 employees. Below that, it suggests a trained first aider from 25 low-hazard or five higher-hazard employees, and an appointed person under those. These are suggestions, not a legal ratio. Your needs assessment sets the number, and HSE says to add cover for absences.
What the law requires, and why it gives no number
The duty is in the Health and Safety (First-Aid) Regulations 1981, which cover every workplace in Great Britain, however small. Regulation 3 asks for "such number of suitable persons as is adequate and appropriate in the circumstances for rendering first-aid to his employees". There's no ratio in it.
Nor does it always ask for a trained first aider. Regulation 3(4) lets you appoint a person to take charge instead, where the work, headcount and location make that adequate. Northern Ireland has its own 1982 Regulations.
HSE's suggested numbers are a starting point, not a legal ratio
HSE's First aid at work: your questions answered (INDG214(rev2), 03/18) says "There are no hard and fast rules on exact numbers" and calls Table 2 "suggestions only". EFAW means emergency first aid at work. "Or part thereof" means round up.
| Hazard level, with HSE's examples | Employees | Suggested first aid personnel |
|---|---|---|
| Low hazard, eg offices, shops, libraries | Fewer than 25 | At least one appointed person |
| Low hazard | 25 to 50 | At least one first-aider trained in EFAW |
| Low hazard | More than 50 | At least one first-aider trained in FAW for every 100 employed (or part thereof) |
| Higher hazard, eg light engineering and assembly work, food processing, warehousing, extensive work with dangerous machinery or sharp instruments, construction, chemical manufacture | Fewer than 5 | At least one appointed person |
| Higher hazard | 5 to 50 | At least one first-aider trained in EFAW or FAW depending on the type of injuries that might occur |
| Higher hazard | More than 50 | At least one first-aider trained in FAW for every 50 employed (or part thereof) |
HSE's wording, INDG214(rev2) Table 2, "Suggested numbers of first-aid personnel to be available at all times people are at work". Accurate as of September 2026.
Construction is on HSE's higher-hazard list, so it suggests a trained first aider on site from five employees, not 25.
Appointed person or first aider: which do you need?
An appointed person takes charge of first aid arrangements, looks after the kit and calls the emergency services. They need no first aid training, and HSE says they "should not attempt to give first aid for which they have not been trained". One should be available whenever people are at work. Regulation 3(3) lets them stand in for an absent first aider only "in temporary and exceptional circumstances", and annual leave doesn't count.
A first aider has trained to the level your needs assessment sets, usually FAW or EFAW. An appointed person who completes EFAW becomes a first aider.
FAW or EFAW: match the training to the injuries
HSE's L74 guidance sets out both.
| Emergency first aid at work (EFAW) | First aid at work (FAW) | |
|---|---|---|
| Length, per HSE | One day | At least three days |
| Covers | Unconsciousness and seizures, CPR and defibrillators, choking, bleeding, shock, minor injuries including minor burns | All of EFAW, plus fractures and spinal injuries, burns and scalds, eye injuries, poisoning, anaphylaxis (severe allergic reaction) and major illness |
From HSE's L74 and first aid FAQs, accurate as of September 2026.
If your work could break bones, injure eyes or cause more than a minor burn, that points to FAW.
Working out your own number
Start from Table 2, then check these factors.
| Factor | What HSE's guidance says to do |
|---|---|
| Shifts and out-of-hours work | Cover whenever people are at work, per shift if needed |
| Several buildings or floors | Consider cover for each building or floor |
| Lone, travelling and remote workers | Consider personal first aid kits and mobile phones |
| Far from emergency services | Tell them your location in writing and plan transport |
| Leave and sickness | Plan cover for planned and unplanned absence |
| Known health conditions | Plan for conditions such as asthma, epilepsy or mental ill health |
| Members of the public | No legal duty, but HSE strongly recommends including them |
From HSE's INDG214 and L74, accurate as of September 2026.
If any row applies, expect a number above Table 2.
One trained person who works weekdays leaves the weekend uncovered. So count the first aiders needed on duty at once, multiply by your shifts, then add cover for leave, the same sum as working out fire cover.
Worked examples: three workplaces, three numbers
These are illustrations, not legal minimums. Each adds one for leave, a rule of thumb for HSE's advice to cover absences, not an HSE figure.
A 30-person office
An office is low hazard, and 30 is in the 25 to 50 band, so HSE suggests at least one EFAW first aider on duty. Add one for leave. Answer: 2 EFAW first aiders.
A construction site with 120 workers
Construction is higher hazard and 120 is over 50, so HSE suggests one FAW first aider per 50 or part thereof, which means three on site at all times. Add one for leave. Answer: 4 FAW first aiders on a single day shift.
That assumes one employer covers all 120, which HSE allows on a shared site. L74 says large sites usually need a first aid room, and flags training for life-threatening bleeding. The CDM Regulations 2015 add no first aid rules. See also The Builders Academy's construction courses.
Two sites with shift working
Say a food factory runs two shifts of 25, with a 15-person office across town. Food processing is higher hazard, its 50 employees sit in the 5 to 50 band, and burns and scalds from hot equipment point to FAW. One per shift, plus one for leave on each, makes four. The low-hazard office is under 25, so an appointed person will do, plus one for leave. Answer: 4 FAW first aiders at the factory and 2 appointed persons at the office.
Certificates, refreshers and records
L74 says FAW, EFAW and other first aid certificates last three years, so retrain before they expire. Once one lapses, the holder is "no longer considered competent to act as a first-aider in the workplace".
INDG214 says "it is strongly recommended that your first-aiders undertake annual refresher training". HSE's FAQs confirm it isn't mandatory.
To show an inspector how you decided, HSE suggests keeping your needs assessment, certification dates, training provider checks and a first aid incident book. None is a legal duty. Regulation 4 only asks you to tell staff the arrangements, and notices do that.
Getting your first aiders trained
HSE accepts blended learning, which mixes e-learning with face-to-face training, and strongly recommends assessing practical skills by direct observation. It stopped approving training providers on 1 October 2013, so checking yours is up to you.
Our first aid training courses cover the theory online, before or alongside the practical training and assessment. The first aid at work e-learning can replace one day of the three-day course, and the emergency first aid at work e-learning two hours of the one-day course. The rest, including the practical assessment, is separate. For wider duties, see The Builders Academy's health and safety courses.
Frequently asked questions
How many first aiders do I need in the workplace?
At least one FAW first aider per 100 employees in low-hazard work, or per 50 in higher-hazard work, above 50. Below that, HSE suggests a trained first aider from 25 low-hazard or five higher-hazard employees, and otherwise an appointed person. These aren't legal ratios.
How many first aiders do I need for 50 employees?
At least one trained first aider on duty, on HSE's numbers. In low-hazard work, HSE suggests EFAW. In higher-hazard work, EFAW or FAW, depending on the likely injuries. At 51, it moves to FAW, which means two in higher-hazard work.
How many first aiders do I need on a construction site?
At least one trained first aider from five employees, then one FAW first aider per 50 or part thereof above 50, so 120 employees means three on site at once. That's HSE's suggestion for higher-hazard work. Under five, an appointed person.
Is it a legal requirement to have a first aider at work?
Not in every workplace. The law asks for adequate and appropriate provision, and regulation 3(4) allows an appointed person instead where the work, headcount and location make that adequate. HSE's minimum is a stocked kit, someone in charge and information for staff.
What is an appointed person for first aid?
Someone who takes charge of first aid arrangements, looks after the kit and calls the emergency services. They need no training, shouldn't give first aid they aren't trained for, and should always be available. They can cover a first aider's unforeseen absence, never annual leave.
What is the difference between FAW and EFAW?
EFAW is one day of emergency first aid, such as CPR, choking, bleeding and minor injuries. FAW takes at least three days, includes all of EFAW, and adds fractures, burns and scalds, eye injuries, poisoning and major illness. Pick by likely injuries.
How long does a first aid at work certificate last?
Three years. HSE's guidance says FAW, EFAW and other first aid certificates all last three years. Once one expires, the holder isn't treated as a competent workplace first aider. HSE puts FAW requalification at two days, so book it early.
Do I need a first aider on every shift?
Yes, if your needs assessment says you need first aiders. HSE says first aid needs to be available whenever people are at work, and each shift may need its own arrangements. If an appointed person is enough, have one on every shift.
Can first aid training be done online?
Partly. The theory can be done online, but the practical assessment can't. HSE expects classroom time for practical skills and strongly recommends assessing them by direct observation, so e-learning alone doesn't make a first aider. The Builders Academy's first aid training courses cover the theory.
How often do first aiders need refresher training?
Once a year is HSE's recommendation, not a legal requirement. INDG214 says annual refresher training is "strongly recommended" to keep basic skills up to date. A refresher doesn't replace requalifying, which every first aider needs before their three-year certificate expires.
What happens if a workplace has no first aid provision?
It's likely breaching the 1981 Regulations, which cover every workplace in Great Britain. HSE deals with breaches proportionately, and enforcement can include a notice or prosecution where warranted. HSE's minimum is an appointed person, a stocked kit and information for staff.
Kerem Ismail is Managing Director of The Builders Academy and has been helping people secure work in the construction industry since 2016.
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