How Many First Aiders Does a Team of 8 Need?
One trained first aider in a team of 8 leaves the site uncovered on about 33 working days a year. A second takes that to 4.2.
More than one. A team of 8 that trains a single first aider has that person absent on about 12.6 percent of working days, which is 33 of the 261 in a year, and on every one of those days the rule "at least one first aider present" is broken. Training a second brings the expected uncovered days down to 4.2, and a third to 0.5. The number that satisfies the rule on paper is one. The number that satisfies it on a Tuesday in August is two, and at this size the difference is one course.
Each extra holder, and what it buys
The rule says 1 first aider present on every working day. Each holder is absent on about 12.6 percent of rostered working days. This is how many working days a year fall short at each holder count.
Holding exactly 1 is a coin flipped every working day. The first spare holder removes most of the exposure; the second removes most of what is left. On these assumptions, 3 holders bring the expected shortfall to one working day a year or fewer, and 4 to one a decade.
How many are actually present
With 1 holder, the average working day has 0.87 present. Averages do not break rosters; the working days with fewer than 1 do. Across 261 working days a year, this is how the year is expected to distribute.
What is hard about this one
A team of 8 is the size where "we have a first aider" is most likely to mean exactly one person, because the team is small enough that one feels proportionate and the person who volunteered is still there. The arithmetic does not care how proportionate it feels. One holder, one required, is a coin flipped every working day with a 12.6 percent chance of coming up empty, and across a year the model expects it to come up empty about 33 times. That is six and a half working weeks of a site that believes it is covered and is not, and nobody notices on any of them unless someone gets hurt.
The second holder is the whole story. With two trained, the site is uncovered only when both are away on the same day, which on independent absences is 1.6 percent of days, or about 4.2 a year. With three it is 0.5 days. Going from one to two removes 87 percent of the exposure; going from two to three removes most of what is left; the fourth buys almost nothing a team of 8 would notice. On a team this size the second certificate is also the cheapest insurance the operation will ever buy, because it costs one day of training and replaces a gap that would otherwise be filled by whoever happens to be standing closest.
What the model does not see is that the single first aider in a small team is rarely just the first aider. The same person tends to be the fire marshal, the keyholder and the one who knows where the spare fuses live, which means their leave takes three qualifications off site at once rather than one. Two holders also protects against the failure the binomial cannot model at all: a certificate that quietly lapsed in March, turning a team that believes it has one into a team that has none until the renewal date. Treat 33 as the floor. The real number is higher every year someone lets the card expire.
Move the requirement, move the answer
The holder count is usually the thing being argued about. The requirement itself is the other lever, and it is worth knowing what the same 1 holders buy if the rule were one looser or one stricter.
| Required present | Covered | Short working days a year |
|---|---|---|
| 1this page | 87.4% | 33 |
| 2 | 0% | 261 |
What this assumes, and where it is generous
These figures treat each holder as independently likely to be absent, which is the assumption most favourable to the roster. Holders are rarely independent: the two people who did the course together take the same school holidays, a certificate that lapses removes someone for the weeks it takes to rebook, and the person who is always asked to cover is the one most likely to be off sick. Treat every number here as the best case.
Only a valid certificate counts. A holder whose certificate has lapsed is a zero in this arithmetic for as long as the renewal takes, so the practical holder count is often one lower than the roster believes, and the row above the one you planned for is the one you are actually living on.
The absence share is 25 days of paid annual leave and 8 days of average sickness per person across 261 working days, which is 12.6 percent of rostered working days. Both inputs vary by country; the relief factor library carries sourced figures for 17 of them. Swap your own in and the shape of the ladder holds even as the counts move.
What to do with this
Train a second first aider before you do anything else about cover, because one holder for one required is uncovered on about 33 working days a year and two holders cut that to 4.2.
Do not let the first aider also be the only keyholder or fire marshal. A single person carrying three qualifications turns one absence into three gaps.
Record the certificate expiry date somewhere the roster can see it. A lapsed card is a zero in this arithmetic, and on a team of 8 it takes the holder count straight back to one.
How long the certificate itself stays valid, and how it is renewed: First Aid at Work (FAW) certificate (United Kingdom, 3 years), Emergency First Aid at Work (EFAW) certificate (United Kingdom, 3 years).
The holder count on this page only works if it is the count of people whose certificate is valid today. Keeping that record current, who holds what, at which level, and until when, is what the Skills tab in Soon is for.
Common questions
- Is one first aider enough for a team of 8?
- Only on paper. A single holder is absent on about 12.6 percent of working days on the assumptions here, 25 days of leave and 8 of sickness, which leaves the site without a first aider on roughly 33 of the 261 working days in a year. Whether that is acceptable depends on the hazard, but it is not what most people mean when they say the team is covered.
- How much does a second first aider change?
- Almost everything. Two holders are both away on the same day about 1.6 percent of the time, which is 4.2 working days a year rather than 33. A third holder takes it to 0.5 days. The second course removes about 87 percent of the exposure; after that the returns shrink quickly.
- What about the days when both first aiders are off?
- At two holders the model expects that on about 4.2 days a year, and that figure assumes their absences are unrelated. If they take the same school holidays, or one covers for the other and burns out, the real count is higher. A third holder, or a standing rule that the two never book the same week, closes most of that gap.
Other qualifications
1 required, 2 held
How Many First Aiders Does a 24/7 Team of 20 Need?1 required, 2 per crew
How Many First Aiders Does a Team of 40 Need for Two on Site?2 required, 4 held
How Many French Speakers Does a Crew of 8 Need for Two on Every Day?2 required, 3 held
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