The sale of vapor extraction systems and oxygen injection systems by a Missouri firm to its clients is exempt from Missouri sales and use tax. Both systems are used to remove pollutants from contaminated groundwater. Equipment used “solely for the purpose of preventing, abating, or monitoring water pollution” is exempt according to Missouri tax code. To claim the tax exemption, the firm must obtain from purchasers a signed Sales/Use Tax Exemption Certificate (Form 149) claiming the exemption for “Air and/or water pollution control machinery, equipment, appliances and devices” and maintain the certificates in its records. The firm is required to collect and remit taxes on the sales of these systems if said certificate is not provided. (Letter Ruling No. LR6637, Missouri Department of Revenue, February 24, 2011)