| FA | Fuel additive |
| FACA | Federal Advisory Committee Act |
| FAIDS | Feline acquired immunodeficiency syndrome |
| FAP | Fixed action pattern |
| FAQ | Frequently Asked Questions |
| FBAS | Fluidized bed asbestos segregator |
| FBC | Fluidized bed combustion |
| FC | Fecal coliform |
| f/cc | Fibers per cubic centimeter |
| FCCU | Fluid catalytic cracking unit |
| FCDs | Flow configuration documents |
| FCE | Full compliance evaluation |
| FCEV | Fuel cell electric vehicle |
| FCL | Family certification level |
| FCO | Federal coordinating officer |
| FCs | Fluorocarbons |
| FD1 | Field duplicate |
| FDA | U.S. Food and Drug Administration |
| FDF | Fundamentally different factor |
| FDMS | Federal Docket Management System |
| FE | Fugitive emission; Iron |
| FEL | Frank effect level |
| FEL (Emission Limit) | Family emission limit |
| FEM | Federal equivalent method |
| Fenton-Driven ISCO | Fenton-driven in-situ chemical oxidation |
| Ferry | Shallow draft vessel |
| FETS | Fire emissions tracking system |
| FEV₁ | Forced expiratory volume |
| FF | Federal facility |
| FF RA | Federal facility remedial action |
| FF RD | Federal facility remedial design |
| FFA Feedstock | Free fatty acid feedstock |
| FFDCA | Federal Food, Drug & Cosmetic Act |
| FFRDC | Federally funded research and development center |
| FFRRO | Federal Facilities Restoration and Reuse Office |
| FFSEP Status Definitions | Federal facilities site evaluation project status definitions |
| FFY | Federal fiscal year |
| FGD | Flue gas desulfurization |
| FGD Wastewater | Flue gas desulfurization wastewater |
| FGEW | Functional group equivalent weight |
| FID | Flame ionization detector |
| FIFRA | Federal Insecticide, Fungicide & Rodenticide Act |
| Filter Profile | Filter |
| FIP | Federal implementation plan |
| FIPS | Federal information processing standards |
| FIRE | Factor information retrieval data system |
| FIRMR | Federal information resources management regulations |
| First Exposure | Exposure |
| FLM | Federal land manager |
| Flow exchange property | Geological |
| FLP | Flash point |
| Fluidized Bed Asbestos Segregator | Sampling |
| Fluorinated GHG Refrigerant | Fluorinated greenhouse gas refrigerant |
| FM | Financial management; Frequency modulation; Friable material |
| FMD | Foot and mouth disease |
| FMFIA | Federal Managers Financial Integrity Act |
| FMVCP | Federal motor vehicle control program |
| FOIA | Freedom of Information Act |
| FONSI | Finding of no significant impact |
| FPMR | Federal property management regulations |
| FPXRF | Field-portable X-ray fluorescence analyzer |
| FQPA | The Food Quality Protection Act |
| FR | Federal Register |
| FR Doc | Federal Register document |
| FRB | Field reagent blank |
| FRC | Federal Radiation Council; Federal records center; Functional residual capacity |
| FRD | Formerly restricted data |
| FRM | Federal reference method |
| FRP | Facility response plan |
| FRS | Facility registry services; Facility registry system |
| FRS ID | Facility registry service ID |
| FS | Feasibility study |
| FSA | Farm Service Agency |
| FSR | Financial status report |
| F&T | Fate and transport |
| FTIRS | Fourier transform infrared spectroscopy |
| FTP | Federal emission test procedure; Federal test procedure; File Transfer Protocol |
| FTP Client | File transfer protocol client |
| Fuel P&D | Fuel processing and delivery |
| Fully Fluorinated GHG | Fully fluorinated greenhouse gas |
| FVC | Forced vital capacity |
| FW | Framework |
| FWPCA | Federal Water Pollution Control Act |