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                                                                   Exhibit 10.18




                      SECOND AMENDMENT TO REVOLVING CREDIT,
                        TERM LOAN AND SECURITY AGREEMENT

         This SECOND AMENDMENT TO REVOLVING CREDIT, TERM LOAN AND SECURITY
AGREEMENT (this "Amendment") is made and entered into this 12th day of November,
1999, by and among AAF-MCQUAY INC., a Delaware corporation "Borrower"); the
various financial institutions listed on the signature pages hereof and their
respective successors and permitted assigns which become "Lenders"; and PNC
BANK, NATIONAL ASSOCIATION, a national association ("PNC"), as collateral and
administrative agent for Lenders (PNC, together with its successors in such
capacity, the "Agent").

                                    RECITALS:

         Agent, Lenders and Borrower are parties to a certain Revolving Credit,
Term Loan and Security Agreement dated September 30, 1999 (as at any time
amended, the "Credit Agreement") pursuant to which Lenders have made certain
revolving credit and term loans to Borrower.

         The parties desire to amend the Credit Agreement as hereinafter set
forth.

         NOW, THEREFORE, for TEN DOLLARS ($10.00) in hand paid and other good
and valuable consideration, the receipt and sufficiency of which are hereby
severally acknowledged, the parties hereto, intending to be legally bound
hereby, agree as follows:

1.                         DEFINITIONS. All capitalized terms used in this
Amendment, unless otherwise defined herein, shall have the meaning ascribed to
such terms in the Credit Agreement.

1.                         AMENDMENTS TO CREDIT AGREEMENT.  The Credit Agreement
is hereby amended as follows:

a.                         By deleting the of Section 7.7 in its entirety and
inserting the following in lieu thereof:

                  7.7 DIVIDENDS. Declare, pay or make any dividend or
         distribution on any shares of the Equity Interests of Borrower (other
         than dividends or distributions payable in its stock, or split-ups or
         reclassifications of its stock) or apply any of its funds, property or
         assets to the purchase, redemption or other retirement of any common or
         preferred stock, or of any options to purchase or acquire any such
         shares of common or preferred stock of Borrower.

a.                         By deleting the of Section 13.2(a) in its entirety
and inserting the following in lieu thereof:

                  (a) TERMINATION BY AGENT. Agent may (and upon the direction of
         the Required Lenders shall) terminate the Agreement without notice upon
         or after the occurrence of an Event of Default; PROVIDED, HOWEVER, that
         the Agreement shall automatically terminate as provided in Section
         11.1(i) hereof.

a.                         By deleting the first paragraph of Section 15.2(b) in
its entirety and inserting the following in lieu thereof:



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                  (b) The Required Lenders, Agent with the consent in writing of
         the Required Lenders, and Borrower may, subject to the provisions of
         this Section 15.2(b), from time to time enter into written supplemental
         agreements to this Agreement or any of the Other Documents executed by
         Borrower, for the purpose of adding or deleting any provisions or
         otherwise changing, varying or waiving in any manner the rights of
         Lenders, Agent or Borrower thereunder or the conditions, provisions or
         terms thereof or waiving any Event of Default thereunder, but only to
         the extent specified in such written agreements; PROVIDED, HOWEVER,
         that no such supplemental agreement shall, without the consent of all
         Lenders:

                           (i)  increase the Commitment Percentage or commitment
                  amount of any Lender;

                           (ii) extend the maturity of any Note or the due date
                  for any amount payable hereunder, or decrease the rate of
                  interest or reduce any fee payable by Borrower to Lenders
                  pursuant to this Agreement or alter the amount of repayments;

                           (iii) alter the definition of the term Required
                  Lenders or alter, amend or modify this Section 15.2(b);

                           (iv) release any portion of the Collateral with an
                  aggregate value in excess of $1,000,000 during any calendar
                  year (other than in accordance with the provisions of this
                  Agreement);

                           (v)  change the rights and duties of Agent;

                           (vi) increase the Maximum Revolving Amount or permit
                  any Out-of-Formula Loan to be made if after giving effect
                  thereto the total of Revolving Advances outstanding hereunder
                  would exceed the Formula Amount for more than thirty (30)
                  consecutive days or exceed one hundred ten percent (110%) of
                  the Formula Amount; or

                           (vii) increase the Advance Rates above the Advance
                  Rates in effect on the Closing Date.

         Any such supplemental agreement shall apply equally to each Lender and
         shall be binding upon Borrower, Lenders and Agent and all future
         holders of the Obligations. In the case of any waiver, Borrower, Agent
         and Lenders shall be restored to their former positions and rights, and
         any Event of Default waived shall be deemed to be cured and not
         continuing, but no waiver of a specific Event of Default shall extend
         to any subsequent Event of Default (whether or not the subsequent Event
         of Default is the same as the Event of Default which was waived), or
         impair any right consequent thereon.

a.                         By changing all references to November 1, 1999 or
December 1, 1999 in Section 6.15 to December 15, 1999.

1.                         RATIFICATION AND REAFFIRMATION. Borrower hereby
ratifies and reaffirms the Obligations, each of the Loan Documents and all of
Borrower's covenants, duties, indebtedness and liabilities under the Loan
Documents.

1.                         ACKNOWLEDGMENTS AND STIPULATIONS. Borrower
acknowledges and stipulates that the Credit Agreement and the other Loan
Documents executed by Borrower are legal, valid and binding obligations


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of Borrower that are enforceable against Borrower in accordance with the terms
thereof; all of the Obligations are owing and payable without defense, offset or
counterclaim (and to the extent there exists any such defense, offset or
counterclaim on the date hereof, the same is hereby waived by Borrower); the
security interests and liens granted by Borrower in favor of Lender are duly
perfected, first priority security interests and liens; the unpaid principal
amount of the Revolving A Advances on and as of the close of business on
November 10, 1999, totaled $52,909,075.17; the unpaid principal amount of the
Revolving B Advances on and as of the close of business on November 10, 1999,
totaled $0.00; and the unpaid principal amount of the Term Loan on and as of the
close of business on November 10, 1999, totaled $29,575,000.00.

1.                         REPRESENTATIONS AND WARRANTIES. Borrower represents
and warrants to Agent and Lenders, to induce Agent and Lenders to enter into
this Amendment, that no Default or Event of Default exists on the date hereof;
the execution, delivery and performance of this Amendment have been duly
authorized by all requisite corporate action on the part of Borrower and this
Amendment has been duly executed and delivered by Borrower; and all of the
representations and warranties made by Borrower in the Credit Agreement are true
and correct on and as of the date hereof.

1.                         BREACH OF AMENDMENT. This Amendment shall be part of
the Credit Agreement and a breach of any of any representation, warranty or
covenant herein shall constitute an Event of Default.

1.                         EXPENSES OF AGENT AND LENDERS. Borrower agrees to
pay, ON DEMAND, all costs and expenses incurred by Agent and Lenders in
connection with the preparation, negotiation and execution of this Amendment and
any other Loan Documents executed pursuant hereto and any and all amendments,
modifications, and supplements thereto, including, without limitation, the costs
and fees of Agent's and Lenders' legal counsel and any taxes or expenses
associated with or incurred in connection with any instrument or agreement
referred to herein or contemplated hereby.

1.                         EFFECTIVENESS; GOVERNING LAW. This Amendment shall be
effective upon acceptance by Agent and Lenders (notice of which acceptance is
hereby waived), whereupon the same shall be governed by and construed in
accordance with the internal laws of the State of New York.

1.                         SUCCESSORS AND ASSIGNS. This Amendment shall be
binding upon and inure to the benefit of the parties hereto and their respective
successors and assigns.

1.                         NO NOVATION, ETC. Except as otherwise expressly
provided in this Amendment, nothing herein shall be deemed to amend or modify
any provision of the Credit Agreement or any of the other Loan Documents, each
of which shall remain in full force and effect. This Amendment is not intended
to be, nor shall it be construed to create, a novation or accord and
satisfaction, and the Credit Agreement as herein modified shall continue in full
force and effect.

1.                         COUNTERPARTS; TELECOPIED SIGNATURES. This Amendment
may be executed in any number of counterparts and by different parties to this
Amendment on separate counterparts, each of which, when so executed, shall be
deemed an original, but all such counterparts shall constitute one and the same
agreement. Any signature delivered by a party by facsimile transmission shall be
deemed to be an original signature hereto.

1.                         FURTHER ASSURANCES. Borrower agrees to take such
further actions as Agent and Lenders shall reasonably request from time to time
in connection herewith to evidence or give effect to the amendments set forth
herein or any of the transactions contemplated hereby.


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1.                         SECTION TITLES. Section titles and references used in
this Amendment shall be without substantive meaning or content of any kind
whatsoever and are not a part of the agreements among the parties hereto.

1.                         RELEASE OF CLAIMS. TO INDUCE AGENT AND LENDERS TO
ENTER INTO THIS AMENDMENT, BORROWER HEREBY RELEASES, ACQUITS AND FOREVER
DISCHARGES AGENT AND EACH LENDER, AND ALL THEIR RESPECTIVE OFFICERS, DIRECTORS,
AGENTS, EMPLOYEES, SUCCESSORS AND ASSIGNS OF LENDER, FROM ANY AND ALL
LIABILITIES, CLAIMS, DEMANDS, ACTIONS OR CAUSES OF ACTION OF ANY KIND OR NATURE
(IF THERE BE ANY), WHETHER ABSOLUTE OR CONTINGENT, DISPUTED OR UNDISPUTED, AT
LAW OR IN EQUITY, OR KNOWN OR UNKNOWN, THAT BORROWER NOW HAS OR EVER HAD AGAINST
AGENT AND EACH LENDER ARISING UNDER OR IN CONNECTION WITH ANY OF THE LOAN
DOCUMENTS OR OTHERWISE. BORROWER REPRESENTS AND WARRANTS TO AGENT AND LENDERS
THAT BORROWER HAS NOT TRANSFERRED OR ASSIGNED TO ANY PERSON ANY CLAIM THAT
BORROWER EVER HAD OR CLAIMED TO HAVE AGAINST AGENT OR ANY LENDER.

1.                         WAIVER OF JURY TRIAL. TO THE FULLEST EXTENT PERMITTED
BY APPLICABLE LAW, THE PARTIES HERETO EACH HEREBY WAIVES THE RIGHT TO TRIAL BY
JURY IN ANY ACTION, SUIT, COUNTERCLAIM OR PROCEEDING ARISING OUT OF OR RELATED
TO THIS AMENDMENT.

         IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
duly executed under seal, and delivered by their respective duly authorized
officers on the date first written above.

ATTEST:                                     AAF-MCQUAY INC.
                                            ("Borrower")


_______________________________             By: _______________________________
   Name:_______________________                 Name:__________________________
   Title:______________________                 Title:_________________________

         [CORPORATE SEAL]

                                            PNC BANK, NATIONAL ASSOCIATION,
                                            as a Lender and as Agent


                                            By:________________________________
                                               Name:___________________________
                                               Title: _________________________