Handy Hint 5 - Always Mix in new bedding, by Dr John Kohnke

If you muck out wet spots and soiled bedding, always mix any new top-ups
of sawdust or shavings by placing it on the cleaned floor area and raking the
slightly soiled bedding over it.
If the bedding is very dusty, then spray it over with a mist of clean water to help settle the surface dust.
Most horses will ‘sniff’ new dry bedding when they are returned to the stable, especially after exercise, and are at risk of deeply inhaling fine dust.
Always try to allow 30 minutes with the doors and/or windows open after mucking out a stable to disperse dust and ammonia gas released from the bedding.

Article courtesy of Dr John Kohnke BVSc RDA - Talking Horses newsletter