Mahogany is actually several different species all sold as Mahogany, All that I have are particularly prone to burning. First while the cut is being made the smoke becomes flame, and worse if a coal gets started it can consume the whole piece by the time you can put it out. The mahogany I have, I have found found to be worse than any other wood I have tried in that regard.
I have found that if you get the wood wet it restrains the laser little but it can keep the smoke from bursting into flame and put a stop to any migrating coals, however the cutting drys that area and so I find that I am running multiple cuts but wetting down the cut between each pass. This has to be done as evenly as possible as less water will cut deeper so the cut will be through in some places and much less in others.
See also Engrave and Cut 1/4" Mahogany tips?