| # | Company name | Role | # of projects |
|---|---|---|---|
| 1 | D & B Fire Sprinkler | Fire protection engineering | 0 |
| 2 | D & C Fire Protection | Fire protection engineering | 0 |
| 3 | D & D Fire Protection | Fire protection engineering | 1 |
| 4 | D & S Fire Protection | Fire protection engineering | 1 |
| 5 | D C Goodman & Sons Inc. | Fire protection engineering | 1 |
| 6 | D. I. Sanitr | Fire protection engineering | 1 |
| 7 | Daart Engineering Co.,inc | Fire protection engineering | 4 |
| 8 | Dabo Fire Protection | Fire protection engineering | 1 |
| 9 | Dacar Fire Protection Inc | Fire protection engineering | 1 |
| 10 | Dallas Fire Protection | Fire protection engineering | 1 |
| 11 | Dalmatian Fire Inc. | Fire protection engineering | 2 |
| 12 | Dalmatian Fire, Inc. | Fire protection engineering | 6 |
| 13 | Dalmatian Fire, Inc. | Fire protection engineering | 3 |
| 14 | Dalmatian Fire, Inc. | Fire protection engineering | 2 |
| 15 | Dalmation Fire Inc. | Fire protection engineering | 1 |
| 16 | Dalmation Fire Inc. | Fire protection engineering | 0 |
| 17 | Dan Woods Fire Protection | Fire protection engineering | 0 |
| 18 | Dan-Car Sprinkler Company | Fire protection engineering | 9 |
| 19 | Davis Ulmer Sprinkler | Fire protection engineering | 1 |
| 20 | Davis Ulmer Sprinkler Co | Fire protection engineering | 1 |