KIRSTY Jones is covered in smuts, her hands are blistered and she's coated in a fine film of oil and coal dust. She is blissfully happy. Kirsty, 33, is a fireman on the North Yorkshire Moors Railway (NYMR). (Someone in their office referred to her as a "firelady" but she just calls herself a fireman.) Steam engines need firemen to shovel the coal in. That's what powers the engine and governs how fast it goes.

"Drivers are the stars, the ones that people always take photos of, but we're the ones in control. We've got the power and they can only go as fast as we let them," says Kirsty.

Especially satisfying, perhaps, when the driver in front is Kirsty's husband David, or her dad, David Jackson. The love of steam trains is definitely a family thing. "We're all mad," says Kirsty cheerfully, "Apart from my mum." Which is probably just as well as she looks after five-year-old granddaughter Lucinda on the days that Kirsty and David are running the trains.

Although there are plenty of women volunteers on the North York Moors Railway, most of them are in fairly traditional roles - catering or in the shop. "Though we have a lady guard who's been there for a long time and we now have two other women who are firemen. But there's not many of us," says Kirsty. "I suppose it's still seen as a very masculine thing."

Certainly, even in these egalitarian days, people are quite surprised when they see Kirsty hard at work, or when she's busy uncoupling the engine. And one or two old fashioned passengers have even grumbled a bit to see a girl doing a man's job.

"I take no notice, because there's only a few of them," Kirsty says. "I suppose that some of them think that if were trying to recreate the 50s and 60s then it's not very authentic. But most people are really great and are just fascinated by what I'm doing. We all share the same enthusiasm, which is what really counts."

Kirsty started in the business young. "My dad is a driver and took me along on the foot plate, so I got a taste for it and I thought I'd have a go, but it was a lot more difficult than I thought," she says.

For a start, you can't just hop on the footplate. You have to be trained, which takes a lot of time. To qualify as a fireman, you have to have done 50 turns alongside a qualified fireman.

"Each turn is really one day. And when you're only there at most twice a month, it takes a long time," says Kirsty. "It took me two years, which is quite quick really but then I went in during holidays as well - anytime I could because that was long before I had a baby."

You start out by cleaning the engines. Not a glitzy or glamorous job.

"You use kerosene and oil and daren't stand near a naked flame when you've finished - and you get blistered and sometimes burnt," Kirsty says.

And all this for the sheer love of it. Kirsty, like so many others who work on the railway, is an unpaid volunteer.

The fireman's work, although very physical, doesn't necessarily require great strength. "Like all things, it's as much about skill, getting the knack of it," Kirsty says. "You don't just throw the coal on, you have to know just where in the firebox to place it, depending on what's needed.

"Then all the engines are different. They all have their characteristics which make them easier or harder to deal with. Sometimes, when I see my name against a particular engine, I groan a bit but it all makes it interesting."

And then there's the days when she has to be there for 5am to get the engine fired up...

The NYMR runs in bad weather too - Santa Specials, then between Christmas and New Year, as well as in October and February half terms when the weather isn't always idyllic.

Back in the real world, Kirsty, who lives in Ruswarp, near Whitby, works for an insurance company in Scarborough, where colleagues have got used to her unusual hobby. "It's a great way to spend your time. And I'd say to any other women who were interested to come on, give it a go. You really feel you've achieved something," she says.

Lucinda is already fascinated by the trains and it's a fair guess that once she's old enough to ride the footplate - 16 - she'll be up there with her mum, dad and granddad.

And yes, one day, Kirsty would like to be an engine driver when she grows up. "Oh yes, I'd like to do it eventually, just to say I'd done it. But really I'm happy being a fireman - that's where the power is," she says.

l The NYMR runs daily until the end of October. Some services may be diesel-hauled. For details, ring (01751) 472508. Talking timetables: (01751) 473535. www.northyorkshirmoorsrailway.com