Amendments can be practical and cost-effective for reducing ammonia [NH3] and greenhouse gas [GHG] emissions from dairy manure. In this study, the effect of 22 amendments on NH3 and GHG carbon dioxide [CO2], methane [CH4] and nitrous oxide [N2O] emissions from dairy manure were simultaneous investigated at room temperature (20°C). Dairy manure slurry (2 kg; 1:1.7 urine:feces; 12% total solids) was treated with various amendments, representing different classes of product, following the suppliers' recommended rates. In this screening of products, one sample of each amendment was evaluated along with untreated manure slurry with repeated measurements over 24 h. Gas emissions were measured after short (3 d) and medium (30 d) storage duration using a photoacoustic multi-gas analyzer. Six amendment products that acted as microbial digest, oxidizing agent, masking agent or adsorbent significantly reduced NH3 by >10% (P = 0.04 to <0.001) after both 3 and 30 d. Microbial digest/enzymes with nitrogen substrate appeared effective in reducing CH4 fluxes for both storage times. Most of the masking agents and disinfectants significantly increased CH4 in both storage periods (P = 0.04 to <0.001). For both CH 4 and CO2 fluxes, aging the manure slurry for 30 d significantly reduced gas production by 11 to 100% (P <0.001). While some products reduced emissions at one or both storage times, results showed that the ability of amendments to mitigate emissions from dairy manure is finite and re-application may be required even for a static amount of manure. Simultaneous measurement of gases identified glycerol as a successful NH3 reduction agent while increasing CH4 in contrast to a digestive-microbial product that significantly reduced CH4 while enhancing NH3 release.