Eight appliances were sent to Ilkley Moor to deal with a blaze measuring 60 metres by 50 metres.
A spokesman said it had caused a lot of smoke and urged people nearby to close doors and windows.
It is the latest in a series of moorland fires in recent days.
Katherine Baldwin said on twitter: “Just looked up as I was driving out from Booths, could not believe my eyes when I saw a blackened smoking area again.
“Awful. I wonder if broken glass is responsible for either fire, there was so much in the Tarn area when I went there last week.”
And Kate Whitham said: “Why does this keep happening? Can’t be standard burning off of the heather if fire engines end up being required surely.”
Beverley Beirne said: “Well, for my two penneth, I don’t believe either of these fires were accidents and it’s not hot enough to just spontaneously start and two accidents in as many weeks is unlikely! Trouble is, if it really has been started on purpose how do you go about stopping this? We can’t patrol the moors day and night!”