| Laboratory Ventilation Control Systems | Landis & Staefa, Inc. |
| Lakos Separators | Dockendorf, W.G., Inc. |
| Lambert Infra-Red Heaters | McClintock & Bustad, Inc. |
| La Salle Air Handlers | JD Sales Co., Inc. |
| Lau Blowers | Haldeman, Inc. |
| Liebert Associates | Liebert Associates |
| Loren Cook Co. | Haldeman, Inc. |
| Louvers | Haldeman, Inc. |
| Louvers (Greenheck) | Airelink Products Corporation |
| Louvers and Dampers | Stark, Carroll G. & Associates |