<PAGE>

                                  Exhibit 31.1

                            CERTIFICATION PURSUANT TO
                                RULE 15d-14(a) OF
                       THE SECURITIES EXCHANGE ACT OF 1934
                             AS ADOPTED PURSUANT TO
                  SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002

I, Michael A. McLain, certify that:

1.   I have reviewed this report on Form 10-Q/A of Aearo Company I;

2.   Based on my knowledge, this report does not contain any untrue statement of
     a material fact or omit to state a material fact necessary to make the
     statements made, in light of the circumstances under which such statements
     were made, not misleading with respect to the period covered by this
     report;

3.   Based on my knowledge, the financial statements, and other financial
     information included in this report, fairly present in all material
     respects the financial condition, results of operations, and cash flows of
     the registrant as of, and for, the periods presented in this report;

4.   The registrant's other certifying officers and I are responsible for
     establishing and maintaining disclosure controls and procedures (as defined
     in Exchange Act Rules 13a-15(e) and 15d-15(e)) for the registrant and we
     have:

               a) designed such disclosure controls and procedures, or caused
          such disclosure controls and procedures to be designed under our
          supervision, to ensure that material information relating to the
          registrant is made known to us by others within those entities,
          particularly during the period in which this report is being prepared;

               b) evaluated the effectiveness of the registrant's disclosure
          controls and procedures and presented in this report our conclusions
          about the effectiveness of the disclosure controls and procedures, as
          of the end of the period covered by this report based on such
          evaluation; and

               c) disclosed in this report any change in the registrant's
          internal control over financial reporting that occurred during the
          registrant's most recent fiscal quarter that has materially affected,
          or is reasonably likely to materially affect, the registrant's
          internal control over financial reporting;

5.   The registrant's other certifying officers and I have disclosed, based on
     our most recent evaluation of internal control over financial reporting, to
     the registrant's auditors and the audit committee of the registrant's board
     of directors (or persons performing the equivalent function):

               a) all significant deficiencies and material weaknesses in the
          design or operation of internal control over financial reporting which
          are reasonably likely to adversely affect the registrant's ability to
          record, process, summarize and report financial information; and

               b) any fraud, whether or not material, that involves management
          or other employees who have a significant role in the registrant's
          internal control over financial reporting.


Date:  November 21, 2005             /s/ Michael A. McLain
                                     ---------------------
                                     Michael A. McLain
                                     Chairman, President and Chief Executive
                                     Officer