178. If a covered facility receives a Safety Data Sheet (SDS) from its supplier that states that the concentration of the TRI substance in the mixture ranges between zero and 10 percent, can the facility estimate the concentration of the TRI chemical in the mixture by using zero as the lower bound?
No, a facility cannot estimate the concentration of a TRI chemical in a mixture by using zero as a lower bound concentration, even if the facility receives an SDS from a supplier stating that the concentration of a TRI substance is between zero and a stated upper bound. If an SDS shows zero as the lower bound of the concentration range, then the lower bound concentration is unknown, and the facility must use the provided upper bound for threshold determinations (40 CFR Section 372.30(b)(3)(ii)). Therefore, in the scenario above, since the facility only knows that the upper bound is 10 percent, it must calculate the amount of TRI chemical in the mixture based on the 10 percent concentration.