Do you even need a CEMS? What the Clean Air Regulations 2014 require before you buy
Buying a CEMS — Part 1 of 5. A practical series for industry, drawn from the DOE CEMS Guidelines (Version 8, 2025), which we helped develop.
A Continuous Emission Monitoring System is a significant investment, and the worst time to discover you’ve bought the wrong one — or skipped a required step — is after it’s bolted to your stack. Before you compare quotes, it’s worth being clear on two things: whether the law actually requires a CEMS at your facility, and what the Department of Environment (DOE) expects you to do before installation.
Are you required to have one?
Under the Environmental Quality (Clean Air) Regulations 2014 (CAR 2014) — made under the Environmental Quality Act 1974 (EQA 1974) — certain stationary emission sources must continuously monitor their emissions. A CEMS isn’t optional decoration; it’s the mechanism that produces a continuous, defensible record proving your stack stays within its limits.
You may be required to install a CEMS if any of these apply:
- Your activity or facility falls under CAR 2014 as a regulated stationary source;
- It’s a condition of your EIA report approval;
- You operate a licensed prescribed premises;
- You’ve been identified as a problematic facility; or
- You’ve received a written directive from DOE under its EQA 1974 jurisdiction.
If you’re unsure which bucket you fall into, that uncertainty is itself a reason to get advice early — the answer shapes everything that follows.
Your activity sets your limits
A common misconception is that there’s a single emission standard for everyone. There isn’t. The 2nd and 3rd Schedules of CAR 2014 specify, by activity type, which pollutants you must monitor (for example total particulate matter, SO₂, NOₓ, CO), the applicable Emission Limit Values (ELVs), and the diluent reference gas (O₂ or CO₂) your readings are corrected to.
This matters before you buy because your activity’s pollutant list and ELV directly determine what analysers and what measuring range your CEMS needs. A system that’s perfect for one industry can be the wrong specification for another. Pin down your pollutants, ELVs and reference gas first — they are the design brief for everything else.
The order of operations the law expects
Here’s the sequence DOE’s guidelines set out — and the steps people most often get wrong by doing them out of order:
- Register as a CEMS Industry with DOE, and apply for CEMS installation through the DOE System for CEMS — before any site installation. Installing first and asking later is the wrong way round.
- Buy a registered, certified system. The CEMS must be MCERT or TÜV QAL1-certified (more on what QAL1 means in Part 2), and it must be supplied and installed by a DOE-registered CEMS consultant — one listed on the DOE website and DOE System for CEMS.
- Match the system to your stack. The consultant is responsible for ensuring the supplied design matches your plant process, flue-gas characteristics, the pollutants you must monitor and your ELV — not just selling a box.
- Have it verified by an independent tester. After installation, a DOE-registered CEMS tester conducts the performance audit. Crucially, the tester must be independent of whoever installed it — they cannot test their own company’s installation.
Who’s who in a CEMS project
It helps to know the four parties you’ll deal with, because their roles are defined and separate:
- CEMS manufacturer — makes the equipment and holds its QAL1 certification.
- CEMS consultant — the DOE-registered company that supplies, installs, commissions and maintains the system, and advises you on compliance. (This is our role.)
- CEMS tester — a separate, DOE-registered party that independently verifies and certifies performance.
- Plant operator — you: responsible for applying to DOE, running the quality-assurance programme, monitoring compliance and reporting.
That separation between installer and tester is deliberate: it’s what makes your compliance data credible to the regulator.
The takeaway
Before you shortlist a single product, you should be able to answer: Am I required to monitor? Which pollutants and ELVs apply to my activity? Have I registered and applied to DOE? Am I buying a QAL1-certified system through a registered consultant? Getting those four right at the start is what keeps a CEMS purchase from becoming a costly do-over.
Not sure where your facility stands? Talk to us — we’ll help you map your obligations before you commit, drawing on the DOE CEMS Guidelines we helped write.
This article is general guidance, not legal advice. For obligations specific to your facility, refer to the current Environmental Quality (Clean Air) Regulations 2014, the EQA 1974, and the DOE CEMS Guidelines, or speak with us directly.
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