Volatile fatty acids (VFAs) are major components of odors associated with agricultural operations and livestock housing, solid waste processing and disposal, industrial and municipal wastewater collection, and treatment systems. Emission estimation and assessment of odor control methods depend on reliable air sampling and analysis methods for VFAs. The objective of this research was to develop and test a method for continuous and reliable generation of standard gas mixtures for VFAs based on permeation tubes. Standard gas mixtures for acetic, propionic, isobutyric, butyric, isovaleric, valeric, and hexanoic acids were generated with permeation tubes and monitored for a 100-day period. The gravimetric loss of VFAs from each tube was measured periodically and used to calculate the emission rate for each permeation tube. Emission rates were as high as 2,011 ng/(min cm) for acetic acid to as low as 49 ng/(min cm) for isovaleric and hexanoic acids. The emission rate was combined with the dilution flow rate to calculate standard concentrations. Five different concentrations for each VFA were obtained by adjusting the dilution flow rate. Gas concentrations were monitored with DVB/Carboxen/PDMS 50/30 .m SPME fibers using triplicate 1 min extractions. Maximum standard gas concentrations ranged from 21.9 ppmv for acetic acid to 0.22 ppmv for hexanoic acid. Minimum standard gas concentrations ranged from 3.0 ppmv for acetic acid to 0.03 ppmv for hexanoic acid. The relative standard deviations (RSDs) for all VFA concentrations ranged from .1.6% to .7.8%. Rapid (1 min) SPME extractions were sufficient to preconcentrate significant amounts of VFAs for separation on a GC-FID without derivatization. The SPME technology proved to be very useful for monitoring standard gas mixtures. Dilution gas flow rate did not affect the emission rates from permeation tubes. In contrast, low acid levels affected permeation rates of the acids from the tubes. The methodology described in this article could be used to generate and test standard gas mixtures for other odorous gases.