the limit of the time-weighted average of the concentration of a chemical agent in the air within the breathing zone of a worker in relation to a specified reference period (unless otherwise specified, occupational exposure limit - a concentration in the workplace air to which most people can be exposed without experiencing harmful effects. There are three different types of exposure limits in commo, Occupational Exposure Limits (OEL's) can be described as limits for airborne concentrations of substances, which are believed to not cause health effects to nearly all workers exposed to those substan, piirnorm - ohtliku aine keskmine kontsentratsioon töökeskkonna sissehingatavas õhus tööpäeva (8h) ja töönädala (40h) jooksul, mis ei kahjusta tervist kogu tööstaaži kestel, kuid ei välista terviserisk, piirnorm - millegi suhtes lubatud kõrgeim määr