Are my ghds faulty?

I've had my ghds for maybe 10 years. The electrics are still working fine (they switch on and heat up fine) but I've noticed that when I get my hair straightened with ghds at a salon, my hair is much smoother and less damaged-looking than when I do it at home. Is it possible there's been some damage that's affected the 'negative ions' technology of the ghds?. I really don't want to fork out for new ones if there's something I can do to fix them. Cheers