BACKGROUND: Most municipalities spend significant resources to control odors from their sewers, but many do not have proof that the product they use is the most effective option. Lexington Fayette Urban County Government (LFUCG) personnel believe that, as much as possible, odor control should be data driven. So rather than rely on recommendations from vendors, they decided to test the effectiveness of multiple chemical(s) in their system. In addition to revealing which chemicals were most effective for odor control, the outcome of this testing revealed unexpected issues from some of the chemicals and unexpected benefits from others. APPROACH: LFUCG selected two of their longest and most odorous force mains (with untreated H2S often over 1,000 ppm). Planning included the establishment of performance goals, identification of data needs, and logistical considerations for chemical implementation. A Request for Proposals (RFP) was issued to invite vendors to pilot test their odor control products. The intent of the RFP was to prequalify multiple, viable vendors. The RFP scope required the provision of chemical, storage tank, feed and control equipment, and H2S monitoring for a 30-day pilot test. Vendors were also responsible for mobilization / demobilization of equipment, delivery and handling of chemicals, safety, maintenance of equipment, H2S monitoring, and reporting of results. LFUCG provided flat gravel areas for the storage tanks, power, access to the wet wells, and a secondary feed point located midway down each force main. RESULTS: Six vendors met the selection criteria so were given a chance to demonstrate the effectiveness of their product. The tested products included: • calcium nitrate, • magnesium hydroxide, • ferrous chloride, • a cellular activation additive, and • a proprietary product (with iron and peroxide). Each vendor was assigned to one of the force mains and was allowed to adjust the chemical dosages to achieve the performance goals. Each vendor started feeding their product following 7 days with no chemical. The products were evaluated based on several criteria: • Did the product achieve the target H2S at the control point? • Was customer service during the pilot project satisfactory? • Does the company demonstrate adequate/reliable company resources? • Is the product compatible with the WWTP operation? • Are there safety concerns regarding handling or spills of the product? • Any concerns regarding storage/mixing (such as freezing)? Ultimately, cost would be a factor for final selection, but the costs proposed for the 30-day pilot testing are not part of the criteria because they are not representative of actual costs for a longer term contract. CONCLUSIONS: Testing revealed that some products were not effective; some products were likely effective but caused operational issues at the receiving treatment plant; and at least one product was effective plus provided operational benefits at the receiving treatment plant. This paper will provide lessons learned about how to perform pilot testing and will share information about the comparison of products.