67 Pa. Code § 449.6
There is no requirement for an escalator clause in any contract. However, if, after reasonable inquiry, the municipality, by resolution adopted at a public meeting, determines that it is unlikely that flat unit price bids will be obtainable for certain materials or equipment, the municipality may prepare and insert an escalator clause in the bid proposal to provide that the price of such materials and equipment will increase or decrease over the bid price if and when the cost to the contractor of the materials and equipment or any material ingredient thereof increases or decreases, as a result of a general price increase or decrease by the supplier of the contractor and in an amount directly related to such increase or decrease. An escalator clause is optional; however, if used, it must be included in the bid proposal prepared by the municipality. An escalator clause may not be inserted by the contractor.
67 Pa. Code § 449.6