TABLE 1 - CRITICAL HEIGHTS (in feet) OF TESTED MATERIALS
	MATERIAL	UNCOMPRESSED DEPTH			COMPRESSED DEPTH
		6 inch	9 inch	12 inch	9 inch
	Wood Chips *	7	10	11	10
	Double Shredded Bark Mulch	6	10	11	7
	Engineered Wood Fibers **	6	7	>12	6
	Fine Sand	5	5	9	5
	Coarse Sand	5	5	6	4
	Fine Gravel	6	7	10	6
	Medium Gravel	5	5	6	5
	Shredded Tires ***	10-12	N/A	N/A	N/A
	* This product was referred to as Wood Mulch in previous versions of this handbook. The term Wood Chips
	more accurately describes the product.
	** This product was referred to as Uniform Wood Chips in previous versions of this handbook. In the
	playground industry, the product is more commonly known as Engineered Wood Fibers.
	*** This data is from tests conducted by independent testing laboratories on a 6 inch depth of uncompressed
	shredded tire samples produced by four manufacturers. The tests reported critical heights which varied
	from 10 feet to greater than 12 feet. It is recommended that persons seeking to install shredded tires as a
	protective surface request test data from the supplier showing the critical height of the material when it
	was tested in accordance with ASTM F1292.
	Table 1 is from the Handbook for Public Playground Safety, publ 325, pg 5, produced by the
	US Consumer Product Safety Commission, Washington, DC 20207
	Definition:
	Critical Height - The fall height below which a life-threatening head injury would not be
	expected to occur, publ 325, pg 2.
	This is also a term used to describe the shock absorbing performance of a surfacing material.
	The surfacing material used under and around a particular piece of playground equipment
	should have a Critical Height value of at least the height of the highest designated play
	surface on the equipment. This height is the fall height for the equipment, publ 325, pg 4.
	Publication available for free online at:		http://www.cpsc.gov/cpscpub/pubs/325.pdf