Smaller compressors are often splash lubricated - the oil is splashed around in the crankcase by the impact of the crankshaft and connecting rods - but larger compressors are likely to have pressurized lubrication using an oil pump which supplies the oil to critical areas through pipes and passages in the castings. Most oil lubricated compressors will have a wet sump at the bottom of the crankcase, and require the oil level to be within limits indicated by a sight glass or dipstick for proper lubrication. The compressor should also be level within the manufacturer's specification while operating. These constraints ensure that the lubricant is in the right place for either the moving parts to contact it for splash lubrication, or for reliable suction to the oil pump. Failure to comply with these specifications can lead to damage to the compressor due to excessive friction and overheating, and contamination of the breathing air by toxic breakdown products of the lubricants.