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MSS: Texas Requirements

In 2008, the Texas Commission on Environmental Quality (TCEQ) set out to discover impediments to meeting the state’s attainment status for National Ambient Air Quality Standards (NAAQS). Their research focused on peak emissions activities in Houston, Galveston, and Brazoria counties. They discovered several undocumented emissions sources, and others that were uncontrolled. Most important, they determined that planned maintenance activities contributed the lion’s share of emissions events. 


This exercise was the genesis of a new set of rules aimed at controlling emissions during planned maintenance: Maintenance, Start-up and Shutdown (MSS) regulations. Enforcement began in 2010, and first focused on Texas refiners. Scheduled roll-outs to other Texas industries culminated in 2015, when MSS regulations became applicable state-wide.


MSS rules revolve around more effective control requirements for all “major” planned maintenance activities, where compounds have a vapor pressure greater than 0.50 psi and a volume greater than 10 cubic feet. Major MSS activities require a Best Available Control Technology (BACT) to capture attendant hazardous vapor streams. Other key elements focus on related monitoring and reporting requirements. MSS rules apply to both permanent and temporary facilities:

Permanent Applications

  • Line breaks

  • Component depressurization and degassing                                                                                                                                                      (towers, vessels, columns, etc.)

  • Pipeline operations

  • Tank operations


Temporary Applications

  • Vacuum truck loading

  • Frac tanks

  • Containers

  • Air movers

  • Abrasive blasting

  • Portable control devices (CAS, internal combustion engines)

  • Temporary control for permanent system outages

    • Flares

    • Thermal oxidizers

    • MVRUs (compressor units)

  • Controlled recovery systems

  • Compressor maintenance

  • Flow-back applications


Emissions from temporary facilities are authorized provided they

  • Do not remain on site more than twelve consecutive months

  • Are used solely to support planned MSS activities

  • Do not operate as a replacement for an existing facility


MSS provides general guidelines for air monitoring equipment and procedures; vacuum truck requirements; and control device requirements. Those general guidelines are often modified according to the specific plant permit.


In general, MSS requires that VOCs be measured using instruments that meet all EPA Method 21 requirements—with a handful of exceptions. Beyond Method 21, MSS guidelines call for monitoring VOC concentrations for at least 5 minutes; for vac truck applications, readings must be taken every 15 minutes. Breakthrough occurs at 100 ppmv.


MSS also prescribes increased recordkeeping, which must be consistent and detailed:

  • Physical location: emission point number, and the common name for the emissions release point

  • Type of activity, and reason for activity

  • Facility I.D. Number, and facility common name

  • Date and duration of activity

  • Estimated quantity of each air contaminant—or mixture of air contaminants—emitted, as well as the data and methods used to determine this information


MSS guidelines have long been well entrenched in downstream markets; in 2012, TCEQ re-wrote guidelines to extend MSS to both midstream and upstream markets. Before, only the Barnett Shale fell under MSS guidelines. MSS guidelines for the broader upstream and midstream markets became effective January 5, 2014. 


The Vapor Point leadership team is your best resource for MSS compliance expertise. Give us a call, and we’ll show you how our VaporLock system can scale to any application that falls under MSS guidelines.

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