| Business | Phone |
| Duke Energy Merchants 10777 Westheimer Rd 650, Houston 77042 | (713) 260-1800 |
| Bayou City Oil & Gas Co 2400 Augusta Dr, Houston 77057 | (713) 278-2300 |
| Bayou City Oil & Gas Co Inc 1201 Louisiana St, Houston 77002 | (713) 651-1116 |
| Calpine Natural Gas 1000 Louisiana St, Houston 77002 | (713) 651-7899 |
| Camfil Farr Indstrl Gas & Air 16011 Aberdeen Forest Dr, Houston 77095 | (281) 861-8488 |
| Camfil Farr Indstrl Gas & Air 17406 Pinecreek Hollow Ln, Houston 77095 | (281) 861-8488 |
| Center Point Energy Entex Po Box 1325, Houston 77251 | (281) 422-8308 |
| Chipawa Gas Corp 3260 Southwest Fwy, Houston 77027 | (713) 621-1818 |
| Cng Energy Svc 4 Greenspoint Mall, Houston 77060 | (281) 874-9151 |
| Falcon Gas Storage Co Inc 1776 Yorktown St, Houston 77056 | (713) 961-3204 |
| Mission Natural Gas 3700 Buffalo Speedway, Houston 77098 | (713) 871-1954 |
| Mid Louisiana Gas Co 1200 Smith St, Houston 77002 | (713) 646-9500 |
| Gas Certification Institute 7979 S Sam Houston Pkwy W, Houston 77085 | (713) 521-9950 |
| H & N Gas Ltd 15333 John F Kennedy Blvd, Houston 77032 | (281) 219-2007 |
| Louisiana Natural Gas 6823 Theall Rd, Houston 77066 | (281) 880-5200 |
| Hgi Corp 10565 Katy Fwy 210, Houston 77024 | (713) 935-9767 |
| Industrial Gas Supply Corp 1600 Smith St 1158, Houston 77002 | (713) 659-1057 |
| Nations Gas 808 Travis St, Houston 77002 | (713) 228-6427 |