translate English to French: With the exception of wood preservation processes, PAHs are typically by-products formed during certain manufacturing and combustion processes, and as such the quantities released as a result of incidental manufacture cannot be determined using engineering calculations or a mass balance.
Il faut au contraire recourir aux mesures directes (systèmes de surveillance en continu des émissions (SCE), contrôle prédictif des émissions ou essais à la source) ou aux facteurs d'émission (propres aux installations ou publiés).