Frequently asked questions
Plain-language answers on continuous and predictive emissions monitoring and the rules behind them. Don't see yours? We'll read your air permit and tell you exactly what it requires.
- What is a CEMS (Continuous Emissions Monitoring System)?
- A CEMS is a hardware-based system — gas analyzers, sample conditioning, stack-flow metering, and data-handling software — that continuously measures the pollutants and diluents leaving a stack. It produces the continuous record used to demonstrate compliance with an air permit and federal rules such as 40 CFR Parts 60, 63, and 75. Trace engineers, builds, installs, certifies, and services complete CEMS in-house.
- What is the difference between CEMS and PEMS — which one do I need?
- A CEMS measures emissions directly with stack analyzers. A PEMS (Predictive Emissions Monitoring System) instead predicts emissions with a software model built from process parameters you already measure, which can cut analyzer and maintenance costs. Which one fits depends on your source, your air permit, and whether your regulator will accept a PEMS. Trace reviews your permit, evaluates the application, and gauges your regulator's buy-in before you commit — no purchase order required.
- What is EPA Performance Specification 16 (PS-16)?
- PS-16 is the EPA performance specification, found in Appendix B to 40 CFR Part 60, that a predictive emissions monitoring system must certify to. It defines how a PEMS is initially validated and the ongoing quality-assurance it must meet — in effect, the standard that governs whether a PEMS is acceptable for compliance. Trace engineered its PEMS around PS-16 and pioneered the first approved PEMS in double-digit U.S. states.
- Does 40 CFR Part 60 require a CEMS?
- It depends on your specific source and subpart. Many New Source Performance Standards (NSPS) under Part 60 require continuous monitoring, but whether that means a CEMS, a PEMS, or another approach is set by the applicable subpart and your air permit. The only reliable answer comes from reading the permit and the rule that applies to your source — which Trace will do for you.
- What is a RATA (Relative Accuracy Test Audit)?
- A RATA is a field test that compares your monitoring system's readings against an independent EPA reference method to confirm the system is accurate. It is required to certify a CEMS or PEMS and to keep it certified through periodic quality assurance, under requirements such as 40 CFR Part 60 Appendices B and F and 40 CFR Part 75. Trace performs and supports RATA testing as part of its service.
- What is a DAHS, and what is Trace DAS?
- A DAHS (Data Acquisition and Handling System) is the software layer that collects signals from your monitors, applies the calculations and averaging your permit requires, stores the records, and generates EPA-ready compliance reports. Trace DAS is Trace's web-based DAHS — the same platform behind every Trace CEMS and PEMS, with fully configurable calculation profiles and access that scales from a single source to a fleet.
- What pollutants and parameters can Trace monitor?
- Across its installations Trace monitors NOₓ, CO, O₂, SO₂, VOCs, total hydrocarbons (THC), and stack flow, plus specialized compounds such as HCl, HF, NH₃, and formaldehyde using FTIR. Systems are matched to the parameters your specific permit and process require.
- Does Trace install and service systems nationwide?
- Yes. Trace is headquartered in Sparta, New Jersey and backs more than 400 installations across the United States with parts, field service, and remote DAS support. Its work spans ethanol, power and behind-the-meter data-center generation, waste-to-energy, chemical, refining, wastewater treatment, marketing storage terminals, and campus combined-utility plants.
Still have a question?
Tell us about your source and permit — we'll tell you exactly what monitoring it requires, with no purchase order needed.