ODS (oxygen depletion system) gas safety heaters/fireplaces. Notice the hole to clean arrows. You can use a straw to blow out the dust or shop air also. When the dust is removed the heater will work properly.I use a product called rust buster.It has a telescoping spout and I shoot a little right into the pilot. I flush it out without messing with the flap on the pilot safety! Bend that flap out and you have screwed up the pilot big time!

 For more info click on the above link to: Pilot keeps going out.