The changing climate, with higher temperatures, is challenging pigs’ abilities to lose metabolic heat.This study was conducted during two summers (2022 and 2023) on a commercial pig farm in Sweden,latitude 59.7°N, using a change over design. In one pig unit the solid floorings, in partly slatted pens(8.96 m2, solid lying area 71% and slatted dunging area 29%), were cooled whilst the solid flooringsin the adjacent pig unit had no cooling. Each pig unit had 38 pens with 9-10 pigs/pen (LYxH, mixedsexes, ~35-115 kg, undocked). Cooling was conducted by circulating chilled water (~11℃) in thewaterborne pipes casted in the concrete. Concentrations of ammonia (NH3) and carbon dioxide(CO2) were measured with a photoacoustic gas monitor 1512 and a multipoint sampler 1409(Lumasense Technologies A/S, Denmark) above four focal pens/pig unit, in addition to samplingpoints by one air inlet and by one exhaust fan in each unit. Temperature and relative humidity werecontinuously registered with loggers (Gemini Data Loggers Ltd., UK) mounted next to the samplingpoints of NH3 and CO2, and close to the lying area in the focal pens. Pig hygiene was assessedaccording to a protocol developed based on literature. Statistical analyses were performed usingPROC GLM in SAS version 9.4. Preliminary results show that the proportion of pigs with the mildesthygiene score (<20 % of the body dirty) were higher in cooled compared to control pens (on average44.6±1.30 vs. 28.8±1.03 % of pigs in the pen (LSM±SE), p<0.001). In accordance, the correspondingproportion of pigs with the most severe hygiene score (>50 % of the body dirty) were lower in cooledpens compared to control (on average 31.8±1.37 vs. 47.9±1.37 % of pigs in the pen (LSM±SE),p<0.001). In addition, the results show lower levels of both NH3 and CO2 with floor coolingcompared to the control (2.9±0.03 vs 4.0±0.03 ppm NH3 and 1345±3.9 vs 1376±3.9 ppm CO2(LSM±SE), p<0.001 for both). The average temperature was lower in the unit with cooled floortreatment compared to control, both in the sample points above the pen (20.7±0.03 vs. 21.2±0.03 ºC(LSM±SE), p<0.001) and closer to the floor in the lying area (26.3±0.06 vs. 27.7±0.07 ºC (LSM±SE),p<0.001) while there were no significant differences in relative humidity between treatments. Theresults indicate a favourable effect of floor cooling on pig hygiene, thermal and gaseousenvironment.