Bias of Tedlar Bags in the Measurement of Agricultural Odorants

Abstract

Odor regulations typically specify the use of dynamic dilution olfactometery (DDO) as a method to quantify odor emissions, and Tedlar bags are the preferred holding container for grab samples. This study was conducted to determine if Tedlar bags affect the integrity of sampled air from animal operations. Air samples were collected simultaneously in both Tedlar bags and Tenax thermal desorption tubes. Sample sources originated from either a hydrocarbon-free air tank, dynamic headspace chamber (DHC), or swine-production facility, and were analyzed by gas chromatography-mass spectrometry-olfactometry (GC-MS-O). Several background contaminants were identified from Tedlar bags, which included the odorous compounds N,N-dimethyl acetamide (DMAC), acetic acid, and phenol. Samples from the DHC demonstrated that recovery of malodor compounds was dependent on residence time in the Tedlar bag with longer residence time leading to lower recovery. After 24 h of storage, recovery of C3-C6 volatile fatty acids (VFA) averaged 64%, 4-methylphenol and 4-ethylphenol averaged 10%, and indole and 3-methylindole were below the detection limits of GC-MS-O. The odor activity value (OAV) of grab samples collected in Tedlar bags were 33 to 65% lower following 24 h of storage. These results indicate that significant odorant bias occurs when using Tedlar bags for the sampling of odors from animal production facilities.

Testing odorants recovery from a novel metallized fluorinated ethylene propylene gas sampling bag

“…The apparent nonequilibrium desorption may lead to interferences with odor samples and may also contribute to variations in sample recovery. This is similar to the results reported by Trabue et al (2006).…”

“…Metallized FEP bags had a significantly cleaner background than that of Tedlar bags, which were contaminated with considerable amounts of DMAC and phenol as well as other interferences containing Si m/z signature ions originating from silicon septum material. Significant amounts of DMAC and phenol in Tedlar bags were previously reported by Koziel et al (2005), Trabue et al (2006), and Mochalski et al (2013).…”

“…Koziel et al reported 32.4% and 77.3% average losses for key odorants of 7 VFAs and 4 semiVOCs after 0.5-hr and 24-hr storage (Koziel et al, 2004). Similar results were reported by Trabue and Anhalt (2006) and Parker et al (2010). Storage of other important air pollutants in CAFOs (H 2 S, NH 3 , and greenhouse gases) in gas sampling bags have been studied by Akdeniz et al (2011).…”

“…Background compounds including phenol, N,N-dimethylacetamide (DMAC), acetic acid, propionic acid, and butyric acid, and other compounds were identified in Tedlar and polypropylene bags Trabue et al, 2006;Parker et al, 2003). Significant sample loss and background emission from Tedlar bags were also reported in studies on human breath constituents (Mochalski et al, 2009(Mochalski et al, , 2013Beauchamp et al, 2008).…”

“…However, most of these odor-causing VOCs are polar, reactive, and highly sorptive onto surfaces of sampling media, which increases the challenge for their measurement. The use of industry-standard Tedlar bags for odor sample collection from CAFOs has been challenged by the evidence of odorous VOC losses and background interferences (Keener et al, 2002a;Koziel et al, 2005;Trabue et al, 2006). It is also known that CAFO odor measurements are often associated with high uncertainties.…”