Nicholas J. Gianoutsos Karl B. Haase 2025 <p><span>This study evaluates the performance of a rigid gas flux chamber equipped with a mass flow meter (MFM) for measuring gas emissions from leaking orphan wells and similar pressure-driven gas point sources. We conducted a series of laboratory and field experiments to evaluate the sensitivity, stability, and dynamic range of an MFM chamber system and found an optimal method for sealing the chamber to the ground to isolate the emission source. From these results, we estimate the effects of different soil gas permeabilities on measurements and identify the uncertainty of environmental processes that can impact measurements. Simulations of an MFM chamber are compared to those of a dynamic flux chamber to contrast the data derived with both methodologies and illustrate the potential for measuring high variability leaks with the MFM chamber. Using a low flow resistance MFM and a chamber well-sealed to the ground, it is possible to measure leaks down to 1.08 x 10^-3</span><span id="MathJax-Element-1-Frame" class="MathJax" data-mathml="&lt;math xmlns=&quot;http://www.w3.org/1998/Math/MathML&quot; id=&quot;M1&quot; display=&quot;inline&quot; overflow=&quot;scroll&quot; dspmath=&quot;mathml&quot;&gt;&lt;mrow&gt;&lt;mn mathvariant=&quot;normal&quot;&gt;1.08&lt;/mn&gt;&lt;mo&gt;&amp;#xD7;&lt;/mo&gt;&lt;msup&gt;&lt;mn mathvariant=&quot;normal&quot;&gt;10&lt;/mn&gt;&lt;mrow&gt;&lt;mo&gt;-&lt;/mo&gt;&lt;mn mathvariant=&quot;normal&quot;&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/mrow&gt;&lt;/math&gt;"></span><span>&nbsp;cubic meters per hour (m</span><span class="inline-formula">³</span><span> h</span><span class="inline-formula">⁻¹</span><span>) (refenced to 25°/1 atm), corresponding to 0.77 grams per hour (g h</span><span class="inline-formula">⁻¹</span><span>) methane or 2.11 g h</span><span class="inline-formula">⁻¹</span><span>&nbsp;carbon dioxide, with a mean uncertainty of 0.89 % relative standard deviation. Environmental processes such as heated gas inside the chamber from solar gain, wind blowing across the chamber vent, and changing humidity in the chamber, can cause variation in MFM measurements. Over 11 d of continuous monitoring under varying weather conditions, the standard deviation of the environmentally sourced signals was found to be 7.40 x 10^-3</span><span id="MathJax-Element-2-Frame" class="MathJax" data-mathml="&lt;math xmlns=&quot;http://www.w3.org/1998/Math/MathML&quot; id=&quot;M6&quot; display=&quot;inline&quot; overflow=&quot;scroll&quot; dspmath=&quot;mathml&quot;&gt;&lt;mrow&gt;&lt;mn mathvariant=&quot;normal&quot;&gt;7.40&lt;/mn&gt;&lt;mo&gt;&amp;#xD7;&lt;/mo&gt;&lt;msup&gt;&lt;mn mathvariant=&quot;normal&quot;&gt;10&lt;/mn&gt;&lt;mrow&gt;&lt;mo&gt;-&lt;/mo&gt;&lt;mn mathvariant=&quot;normal&quot;&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/mrow&gt;&lt;/math&gt;"></span><span> m</span><span class="inline-formula">³</span><span> h</span><span class="inline-formula">⁻¹</span><span>&nbsp;(equivalent to or 5.27 g h</span><span class="inline-formula">⁻¹</span><span>&nbsp;methane or 14.45 g h</span><span class="inline-formula">⁻¹</span><span>&nbsp;carbon dioxide). Strategies to obtain the highest quality data from MFM chambers include burying the edges of the chamber below the surface sufficiently deep to seal the chamber edges against gas flow and soaking the dirt with water to lower the chances of escaping gases, while monitoring the gas flow and adjusting the chamber seal to achieve a maximum flow rate.</span></p> application/pdf 10.5194/amt-18-4207-2025 en European Geosciences Union Evaluating mass flow meter measurements from chambers for greenhouse gas emissions from orphan wells and other point sources article