I don't know about sulfur but seven dust is great for fleas.
Will sulfur kill fleas
It works but as was stated it's not good for you or those around you. Look for alternative methods to rid your yard of fleas.
It's not environmentally friendly for you and for the surrounding place. Research environmental friendly tips
Sulfur is definitely not environmentally friendly
You can but I found out that it did not work so I got a bottle of Malathion from the feed store and mixed it 3/4 to 1/4 of water and it worked for me.