---
title: "Total Reduced Sulphur (TRS)"
description: "Total Reduced Sulphur (TRS) is the aggregate emissions metric that adds up the reduced-sulphur compounds released from kraft pulping — hydrogen sulphide (H₂S), methyl mercaptan (CH₃SH), dimethyl sulphide ((CH₃)₂S) and dimethyl disulphide ((CH₃)₂S₂). TRS is the signature emissions-and-odour metric regulated for kraft mills under most jurisdictions' permit conditions."
canonical_url: "https://sylio.co/glossary/trs-total-reduced-sulphur"
last_updated: "2026-06-28T02:29:36.504Z"
---

**Total Reduced Sulphur (TRS)** is the aggregate emissions metric that adds up the reduced-sulphur compounds released from kraft pulping — hydrogen sulphide (H₂S), methyl mercaptan (CH₃SH), dimethyl sulphide ((CH₃)₂S) and dimethyl disulphide ((CH₃)₂S₂). TRS is the signature emissions-and-odour metric regulated for kraft mills under most jurisdictions' permit conditions.

## Sources of TRS

- [Recovery boiler](/glossary/recovery-boiler) flue gas (during upsets or poor combustion)
- [Lime kiln](/glossary/lime-kiln) flue gas
- Brown stock washers and diffusers
- Black-liquor evaporators
- Smelt-dissolving-tank vent

## Cleaning relevance

TRS is fundamentally a combustion-control and operating-discipline problem, not a cleaning problem. However, well-cleaned recovery boilers and lime kilns operate more stably and produce lower TRS excursions during transient operation. Continuous [sonic-horn](/glossary/sonic-horn) cleaning indirectly supports TRS compliance by preserving stable boiler operation.

## Related terms

- [Recovery boiler](/glossary/recovery-boiler)
- [Lime kiln](/glossary/lime-kiln)