9 CFR §310.13

1. (a)Establishments that slaughter livestock and prepare livestock carcasses and parts may inflate carcasses or parts of carcasses with air if they develop, implement, and maintain controls to ensure that the air inflation procedure does not cause insanitary conditions or adulterate product. Establishments shall incorporate these controls into their HACCP plans or Sanitation SOPs or other prerequisite programs.
2. (b)
   1. (1)Transferring the caul or other fat from a fat to a lean carcass is prohibited.
   2. (2)Injecting compressed air into the skulls of cattle in conjunction with a captive bolt stunner to hold the animal still for dressing operations is prohibited.