Mental health first aid in the workplace: who picks up the call when your one trained first aider is on annual leave?

What one trained first aider actually covers

Take one site with one trained mental health first aider. On the days they are in, a colleague who decides to talk has someone trained to go to. On every other day there is nobody, and those days add up quickly.

On the legal minimum alone, the one trained person is entitled to 5.6 weeks’ paid holiday a year, and whenever they take it while the site is open, nobody trained is on it. That is the statutory floor, not a measure of the leave people actually take.

Then add ordinary working life. A first aider on three days a week covers three days. One who works weekday days covers nobody on the night shift or at weekends. One at head office can help someone at the depot only if that person knows to pick up the phone. Sickness takes them out without notice.

HSE already expects physical first aid to survive this. Its first-aid guidance says employers need to ensure there is cover for annual leave and other planned absences of first aiders, and that separate arrangements may have to be made for each shift. In 2024 HSE reissued the same guidance to emphasise that employers take account of employees’ mental health in their first-aid needs assessment. HSE does not say mental health first aiders need holiday cover; that step is ours. But once mental health sits in the same assessment, it is hard to argue that its cover should vanish whenever one person books a holiday.

How many mental health first aiders does a workplace need?

It is usually the first question about mental health first aid in the workplace, and the two bodies you might expect to answer it both point back to your own organisation.

MHFA England’s current guide for employers asks you to consider your organisation’s structure and the demands on your workforce. For multisite organisations it says it is important that a mental health first aider is always available at each location. And it suggests that for some organisations “it may be worthwhile” aiming to have as many mental health first aiders as physical first aiders.

HSE’s first aid page for employers lists appointing mental health trained first aiders as one of several ways to manage mental ill health, alongside information or training for managers and employees, occupational health and employee support programmes. Of first aid in general, it says HSE cannot tell you what provision you should make and that there are no hard and fast rules on exact numbers. Mental health first aiders are not a legal requirement.

So the number has to come from your own rota. Our suggestion for a floor: at least two in-date trained names on every site and every shift, with their leave booked so they are not away in the same weeks. Two, because one leaves a gap every time that person is off.

That is a floor, and what sits above it comes down to demand and choice: a large site can bring more conversations than two people could hold alongside their day jobs, and someone who is struggling will talk to some colleagues and not others. Equally, a single-site office working weekday days, with two trained people on different leave, may already be at its floor.

Who someone talks to when the first aider is away

The call in the title is not a phone line. It is the moment someone decides to tell a person at work that they are not coping. Mental health first aid is not an on-call service: MHFA England’s guide says first aiders should only make themselves contactable during work hours and should not give out personal contact details. If the trained colleague someone had in mind is on leave, three routes are worth making sure of.

• A second trained name on the same site and shift. Publish both names with where and when each works, and ask first aiders to say when they are away.
• Someone outside their own team. Some people will not talk to anyone who sits beside them or shares their manager. A trained colleague at another site, reachable by phone or video in working hours, gives them another option.
• Their line manager. A line manager may be the first to hear it, trained or not, which is why we have written separately about what managers need when someone raises their mental health.

Tell staff plainly that first aiders are available in working hours only, and put the out-of-hours routes beside their names.

How cover shrinks after the training, and how to keep it

A count of trained names is right only until the rota changes. Mental Health First Aid training is valid for three years, and MHFA England recommends a refresher every three years to renew it. Its guide for employers also asks organisations to review the position when people leave and to train more people to maintain numbers.

The triggers are ordinary rota changes: a first aider resigns, moves site, swaps to nights or starts a long stretch of leave. Each one can empty a slot, so re-run the count whenever one happens.

When the count comes up short, the time cost is easy to work out. Mental Health First Aid is a two-day course, so each new first aider is two days out of the business, and one cohort takes up to 16 people.

Our guide How much mental health cover does your organisation need? Ratios, rotas and cost turns this into a step-by-step method for your own sites and shifts, including where the ratio figures you may have seen come from. For what keeps trained first aiders active once the course is over, see our post on running a mental health first aiders programme.