Substances having spontaneous Ignition hazard assigned with EmS spillage code S-M in IMDG Code do not have any spillage control measure as these substances when spilled may ignite within 5 minutes after contact with air. Hence response to spillage is firefighting.
Example UN 3394 ORGANOMETALLIC SUBSTANCE, LIQUID, PYROPHORIC, WATER-REACTIVE – Class 4.2/4.3
See entry in IMDG Code & EmS Guide below