Air Change Index

The Air Change Index (ACI) model was developed to rapidly assess the potential for solvent vapors released from solvent-borne paints to exceed the OEL (Occupational Exposure Limit) during indoor painting.

The Air Change Index gives a prediction of the number of air changes needed to ensure that the peak solvent vapor concentration remains below the OEL of the solvent when applying one liter of paint under standard conditions.

Standard conditions are defined as an ambient temperature of 20C, a room volume of 100 m3, and a paint coverage of 10 m2/L. The ACI can be calculated for any set of conditions, with the appropriate changes in the formula:

An ACI lower than 1 means that the volume of air in the room is enough to keep the solvent vapors below the OEL, thus corresponding to zero air renewal. Above 1, the ACI value gives an indication of the number of air renewals required to work safely with one liter of paint without exceeding the OEL. However, ventilation is always recommended.

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