Hang the chain up or stretch the chain out on a level floor in a well-lighted area. Remove all twists. Measure the sling length. Discard if a sling has been stretched. Twisted or bent.
Links tend to close up and get longer.
Check master link, load pins and hooks for any of the above faults. Manufacturers' reference charts show sling and hitch capacities. Record manufacturer, type, load limit and inspection dates. Find out load weight before lifting. Lower working a load limit if there may be severe impact.