| 1549 | Infant and junior food, canning | |
| 3311 | Infant incubators, manufacturing | |
| 5232 | Infants and toddlers clothing, retail | |
| 1531 | Infants' cereals, dry, manufacturing | |
| 1810 | Infants' clothing, cut and sewn from materials owned by others | |
| 1810 | Infants' clothing, cut and sewn from purchased fabric | |
| 1730 | Infants' clothing, made in knitting mills | |
| 5131 | Infants' clothing, wholesale | |
| 1549 | Infants' formulas, manufacturing | |
| 5232 | Infants' wear stores, retail | |
| 5131 | Infants' wear, wholesale | |
| 7512 | Infectious diseases quarantine enforcement, federal administration | |
| 7523 | Inferior courts | |
| 8519 | Infirmary, providing personal nursing care | |
| 6420 | Information access services, on-line | |
| 7230 | Information management system design services, computer | |
| 6309 | Information service, freight rate | |
| 3150 | Infra red lamps, manufacturing | |
| 3312 | Infrared analytical instruments, laboratory type, manufacturing | |
| 3312 | Infrared homing systems, aeronautical, manufacturing | |
| 3313 | Infrared instruments, industrial process type, manufacturing | |
| 3150 | Infrared lamp bulbs, manufacturing | |
| 3150 | Infrared lamp fixtures, manufacturing | |
| 2914 | Infrared ovens, industrial process type, manufacturing | |
| 3210 | Infrared sensors, solid state, manufacturing | |
| 2720 | Ingot, made by rolling purchased aluminum | |
| 2710 | Ingot, made in steel mills | |
| 2720 | Ingot, primary aluminum, manufacturing | |
| 5142 | Ingots (except precious), wholesale | |
| 5142 | Ingots, non-ferrous metals, wholesale | |
| 2720 | Ingots, primary, nonferrous metals (except aluminum, copper), manufacturing | |
| 4520 | In-ground swimming pools, residential, installation | |
| 8519 | Inhalation therapists, registered | |
| 3311 | Inhalation therapy equipment, manufacturing | |
| 3311 | Inhalators, surgical and medical, manufacturing | |
| 2429 | Inhibitors (e.g., corrosion, oxidation, polymerization), manufacturing | |
| 2929 | Injection moulding machinery for plastics, manufacturing | |
| 2520 | Injection moulding plastic products | |
| 2424 | Ink eradicators, manufacturing | |
| 2422 | Ink jet cartridges, recycling (i.e., cleaning and re-filling) | |