The fire broke out at Crawley Hospital in West Green Drive, Crawley at 13.36 pm.
It's believed to be in a sixth floor store room. There are no reports of casualities.
50 firefighters are involved with tackling the blaze.
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Fifth generation market trader Wayne Bellows has been told he makes too much noise trying to sell fruit and veg from his stall.
The fire was started accidentally when oil ignited in front of a resident while he was cooking.
Holly Green has the forecast