Are the quantities of different hazardous constituents additive?

In determining whether a Reportable Quantity (RQ) has been released, are the quantities of different hazardous constituents additive under the mixture rule?

No. RQs of different substances are not additive under the mixture rule; releasing a mixture containing half an RQ of one hazardous substance (other than radionuclides) and half an RQ of another hazardous substance does not require a report.