| # | Company name | Role | # of projects |
|---|---|---|---|
| 1 | L & K Fire Protection | Fire protection engineering | 1 |
| 2 | L Pugh & Associates | Fire protection engineering | 2 |
| 3 | L. M. Erikson | Fire protection engineering | 1 |
| 4 | Lafayette Fire & Safety Inc | Fire protection engineering | 2 |
| 5 | Landmark Contracting/Fire Protection Inc. | Fire protection engineering | 1 |
| 6 | Landmark Sprinkler Inc | Fire protection engineering | 1 |
| 7 | Larden Muniak Consulting Inc. | Fire protection engineering | 16 |
| 8 | Leduc & Dexter Plumbing | Fire protection engineering | 1 |
| 9 | Life Safety Designs | Fire protection engineering | 3 |
| 10 | Life Safety Systems Inc. | Fire protection engineering | 0 |
| 11 | Lifeguard Fire Protection, Inc. | Fire protection engineering | 2 |
| 12 | Link-nilsen Corp (fire Protection | Fire protection engineering | 1 |
| 13 | Livingston Fire Protection Inc | Fire protection engineering | 0 |
| 14 | Locke & Locke Inc. | Fire protection engineering | 0 |
| 15 | Locke Carey | Fire protection engineering | 13 |
| 16 | Locke Carey | Fire protection engineering | 0 |
| 17 | Locke Carey Elmark | Fire protection engineering | 0 |
| 18 | Lone Star Sprinklers | Fire protection engineering | 1 |
| 19 | Los Angeles Fire Detection | Fire protection engineering | 1 |