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D5835-20 – Standard Test Method Technical Guide
🎯 Scope and Applicability of D5835-20
ASTM D5835-20 is a standard practice that provides procedures and equipment for the representative automated sampling of effluent gas streams. It specifically covers the determination of Oxygen (O₂), Carbon Dioxide (CO₂), Carbon Monoxide (CO), Sulfur Dioxide (SO₂), Nitric Oxide (NO), Nitrogen Dioxide (NO₂), and Total Oxides of Nitrogen (NOₓ).
The standard’s applicability is limited by certain combustion processes and conditions. Caution and competent technical judgment are required for corrosive or highly reactive components, high vacuum, high pressure, or high temperature streams, wet flue gases, fluctuating process conditions, gas stratification, and low concentration measurements.
| 🟦 Gas Constituent | 📏 Common Source | 🎯 Applicability Note |
|---|---|---|
| O₂, CO₂, CO | Combustion Efficiency | Standard Application |
| SO₂, NOₓ | Fossil Fuel Combustion | Standard Application |
| Corrosive Components | Chemical Processing | Requires Special Handling |
⚙️ Sampling Strategies: Extractive and Non-Extractive Systems
The practice details two primary sampling approaches. In extractive sampling, the gas is removed from the duct, conditioned to remove aerosols, particulate matter, and other interfering substances, and then conveyed to the automated analyzers. Non-extractive (in-situ) sampling measures the gas concentration directly within the stack without extraction.
While the practice focuses on gas concentration sampling, it explicitly notes that velocity measurements—which are required to determine mass flow rates—are not included. Refer to ASTM D3154 or 40 CFR Part 60, Appendix A methods for these measurements.
⚠️ Critical Process Limitations
Processes involving wet flue gases, high temperature streams, or significant fluctuations in velocity and concentration require highly competent technical judgment. The standard emphasizes that gas stratification due to the non-mixing of streams represents a particularly challenging condition for achieving representative sampling.
📏 Referenced Documents and Compliance Framework
D5835-20 references several key ASTM and EPA standards. These documents provide the foundational terminology, alternative test methods, and regulatory context required for comprehensive compliance testing of stationary source emissions.
| ⚡ Standard / Regulation | 📐 Role in D5835-20 |
|---|---|
| ASTM D1356 | Terminology for sampling and analysis |
| ASTM D3154 | Average velocity in a duct (Pitot tube) |
| 40 CFR Part 60 App A | Methods 2, 3, 3a, 6, 6c, 7, 7e, 10 |
💡 Technical Best Practice
For extractive sampling, the conditioning system is paramount. Ensure complete removal of aerosols and particulate matter to prevent interference with automated analyzers. Always consult the specific safety precautions listed in Sections 5.1.4.8, 5.2.1.6, and 6.2.2.1 of the standard before system operation.
❓ Frequently Asked Questions
🔍 What specific gas constituents are covered under ASTM D5835-20?
This practice covers the automated determination of Oxygen (O₂), Carbon Dioxide (CO₂), Carbon Monoxide (CO), Sulfur Dioxide (SO₂), Nitric Oxide (NO), Nitrogen Dioxide (NO₂), and Total Oxides of Nitrogen (NOₓ).
💡 What are the primary differences between extractive and non-extractive sampling?
Extractive sampling removes the gas from the stack and conditions it for external analysis. Non-extractive (in-situ) sampling measures the gas concentration directly within the stack without removing a sample.
⚡ Does this standard provide procedures for measuring gas velocity or mass flow rates?
No. The standard explicitly excludes velocity measurements, which are required for determining mass flow rates. Users must consult other standards such as ASTM D3154 or 40 CFR Part 60 Appendix A methods for this purpose.
📌 What process conditions significantly limit the applicability of this practice?
Limiting conditions include corrosive or highly reactive components, high vacuum or high pressure streams, high temperatures, wet flue gases, excessive fluctuations, gas stratification, and very low gas concentrations.