OSHA standards do not specify a minimum diameter for caps used to eliminate impalement hazards. The cap must be large enough to dissipate the forces of impact to prevent impalement from a reasonably foreseeable fall distance. It should be noted that the use of impalement protection caps is but one method of protection; covers or wooden troughs can be another means of meeting the guarding requirement. OSHA considers protective devices (covers or wooden troughs) for rebar that are capable of withstanding at least 250 pounds dropped from a height of 10 feet to be adequate.