Environment Agency MATS (Mercury and Air Toxics Standards) Compliance for Coal Plants

A coal unit doesn't fail a stack test because the technology can't do the job. It fails because a sorbent injection rate drifted, a CEMS calibration lapsed, or a mercury monitor's quality-assurance check got pushed back a week and never rescheduled. Sign up to run your MATS compliance program — mercury sorbent systems, PM controls, acid gas scrubbing, and CEMS calibration — from one CMMS that keeps every reading, every calibration, and every maintenance record audit-ready.

Why It Matters

MATS was built around a simple idea: mercury and acid gases don't stay near the stack, they travel into water, soil, and food chains. A coal plant can run its scrubber and sorbent injection system every day of the year and still fail an audit if the calibration logs, stack test records, and maintenance history aren't there to prove it. The equipment doing the work and the paperwork proving it worked are two separate jobs, and most compliance gaps come from the second one, not the first.

The Three Pollutants MATS Was Written Around

Mercury

Controlled through activated carbon or sorbent injection, tracked against emission limits that vary by unit design, coal rank, and whether the unit burns lignite.

Particulate Matter

Used as a surrogate for non-mercury metals like arsenic, chromium, and nickel, verified through periodic stack testing or continuous monitoring depending on the compliance path chosen.

Acid Gases

Hydrogen chloride and hydrogen fluoride limited through scrubbers or dry sorbent injection, with sulfur dioxide accepted as an alternate compliance surrogate for HCl.

Every unit has to pick a monitoring path for each pollutant — continuous emissions monitoring, sorbent trap monitoring, or periodic stack testing — and that choice determines what gets logged daily versus what gets verified quarterly. Mixing up the schedule for one unit with another is one of the fastest ways a compliance team loses track of what's actually due.

Where MATS Programs Actually Break Down

Missed Calibrations

A CEMS or mercury monitor running past its calibration window quietly invalidates every reading it takes until it's fixed

Sorbent Drift

Injection rates tuned for one coal blend and never re-checked after a fuel switch is a common, avoidable exceedance

Stack Test Gaps

A periodic test that slips past its window looks identical to a unit that was never tested at all

Startup/Shutdown Blind Spots

Emissions during transitions get logged inconsistently even though they're where limits are hardest to hold

Scattered Records

Calibration sheets, sorbent logs, and lab results split across spreadsheets nobody can produce together on request

Unit-Level Confusion

Applying one unit's monitoring path or limit to another unit on the same site is a finding waiting to happen

Never Let A Calibration Or Sorbent Check Slip Again

Oxmaint tracks every CEMS calibration, sorbent injection check, and stack test against its own MATS deadline, flags anything approaching its window, and keeps the evidence attached and searchable. Sign up for a free trial to run it on your own units, or book a demo to see it set up for your fleet.

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Why The Rulebook Just Shifted Under Coal Plants

In February 2026, EPA repealed the 2024 MATS amendments and reinstated the original 2012 standards, removing the tighter filterable PM limit, the stricter lignite mercury standard, and the PM CEMS requirement that plants had only recently started building compliance programs around. That reversal is already being challenged in court by a coalition of states and public interest groups, which means the rules a plant is designing its program to could shift again before the next permit cycle. A maintenance program built around whatever the current limit happens to be is fragile. One built around tracking every unit's actual monitoring path, calibration history, and test results holds up no matter which version of the standard is in effect.

Monitoring Path By Pollutant

Pollutant	Typical Monitoring Path	What Gets Verified
Mercury	Sorbent trap or continuous mercury monitor	Injection rate, trap results, calibration accuracy
Particulate matter	Periodic stack test or PM CEMS	Filterable PM against unit-specific limit
Acid gases	HCl CEMS or SO2 as surrogate	Scrubber or DSI performance against limit

Frequently Asked Questions

Q Which power plants does MATS actually apply to?

Coal- and oil-fired electric utility steam generating units above 25 megawatts that sell power to the grid, whether utility-owned or independent power producers, with a handful of narrow exemptions for units that rarely operate.

Q Does a missed calibration always mean an exceedance?

Not necessarily, but it means the readings during that gap can't be relied on as valid data, and regulators generally treat unverifiable monitoring the same way they'd treat a missing record — as a problem until proven otherwise.

Q How does a plant keep up if the standard keeps changing?

By tracking the underlying maintenance and monitoring activity — calibrations, sorbent checks, stack tests — against whichever limit is currently in force, rather than rebuilding the tracking system every time the regulation itself moves.

Walk Into Your Next Stack Test With A Clean Record

Oxmaint keeps mercury monitoring, sorbent injection, PM controls, and acid gas scrubbing tied to their unit, their deadline, and their evidence, all in one auditable log. Sign up for a free trial to run it on your own units, or book a demo to see it configured for your fleet.

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