| PrimaryDivision | FourLetterDesignation | DepartmentName | County |
| 4 | ABBO | Abbott Park Fire Protection | Lake |
| 4 | ABBO | Abbott Laboratories | Lake |
| 31 | ABGD | Abingdon Fire Protection District | Knox |
| 12 | ADSN | Addison Fire Protection District | DuPage |
| 38 | ADVN | Advance EMS of Dixon | |
| 57 | AFPD | Arlington Fire Protection District | Bureau |
| 35 | AHFD | Alhambra | |
| 1 | AHTS | Arlington Heights Fire Department | Northwestern Cook |
| 36 | AKPR | Akron-Princeville FPD | Peoria |
| 997 | ALBN | Albany Fire Department (WI) | Green |
| 30 | ALBY | Albany Fire Department | |
| 39 | ALED | Aledo Fire Protection District | |
| 39 | ALEX | Alexis Fire Protection District | Warren and Mercer |
| 35 | ALFD | Alton Fire Department | |
| 2 | ALGN | Algonquin/Lake in the Hills Fire Protection Dist. | Kane |
| 31 | ALNH | Alexis North Henderson Fire Protection District | |
| 32 | ALOR | Alorton Fire Department | St. Clair |
| 28 | ALRT | Allerton Fire Protection District | Champaign |
| 22 | ALSP | Alsip Fire Department | South Cook |
| 31 | ALTA | Altona Fire Protection District | |
| 54 | ALTM | Altamont Fire Protection District | Effingham |
| 25 | ALTW | Allen Township Fire Protection District | LaSalle |
| 38 | AMBY | Amboy Fire Protection District | Lee |
| 104 | AMRF | Amr of Ft. Atkinson | Jefferson |
| 41 | ANCH | Anchor Fire Department - Octavia FPD | McClean |
| 39 | ANDU | Andulusia Fire Protection District | Rock Island |
| 45 | ANNA | Anna Fire Department | Union |
| 39 | ANWN | Annawan - Alba Fire Department | Henry |
| 26 | ARCO | Arcola Fire Protection District | Douglas |
| 107 | ARES | 440th Air Reserve Station | Milwaukee |
| 10 | ARGN | Argonne Fire Department | Western Cook |
| 997 | ARGY | Argyle Fire Department | Green |
| 44 | ARNZ | Arenzville Fire Department | Cass |
| 7 | AROM | Aroma Fire Protection District | Kankakee |
| 46 | AROR | Argenta/Oreana Fire Protection District | Macon |
| 28 | ARRW | Arrow Ambulance | |
| 26 | ARTH | Arthur Fire Department | |
| 42 | ARTN | Armington Fire Protection District | Tazewell |
| 47 | ASHL | Ashley Community Fire Protection District | |
| 37 | ASKM | Ashkum Fire Protection District | |
| 50 | ASPN | Assumption Fire Protection District | Christian |
| 38 | ASTN | Ashton Fire Protection District | Lee |
| 4 | ATIO | Antioch Fire Department | North Lake |
| 39 | ATKN | Atkinson Fire Department | Henry |
| 26 | ATWD | Atwood Fire Protection District | |
| 13 | AURA | Aurora Fire Department | Kane |
| 47 | AVIS | Aviston Fire Protection District | |
