Document:

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                                                                    EXHIBIT 10.2

                      FIFTH AMENDMENT TO REVOLVING CREDIT
                        AND LETTER OF CREDIT AGREEMENT
                        ------------------------------

     THIS FIFTH AMENDMENT is made effective as of the 18th day of May, 2000 by
and among ENVIRONMENTAL ELEMENTS CORPORATION, a Delaware corporation
("Borrower") and MERCANTILE-SAFE DEPOSIT AND TRUST COMPANY, a Maryland banking
corporation ("Bank").

                                    RECITALS
                                    --------

     A.  The Bank previously agreed to extend credit to the Borrower pursuant to
a certain Revolving Credit and Letter of Credit Agreement dated November 24,
1993, as amended by a letter agreement dated May 26, 1994 from Nicholas C.
Richardson to Thomas B. McCord, a Second Amendment to Revolving Credit and
Letter of Credit Agreement dated October 25, 1995, a Third Amendment to
Revolving Credit and Letter of Credit Agreement dated June 12, 1998, and a
Fourth Amendment to Revolving Credit and Letter of Credit Agreement dated August
31, 1999 (collectively, the "Agreement"), in the form of a line of credit
facility in an original principal amount not to exceed Ten Million Dollars
($10,000,000.00), which was subsequently reduced to Seven Million Dollars
($7,000,000.00), then increased to Twelve Million Dollars ($12,000,000.00), and
subsequently increased again to Fifteen Million Dollars ($15,000,000.00).

     B.  The indebtedness under the Agreement is evidenced by a Line of Credit
Promissory Note dated November 24, 1993 from Borrower to Bank, as modified by a
certain First Amendment to Line of Credit Promissory Note dated October 25,
1995, certain letter agreements between the Bank and  Borrower, a certain Second
Amendment to Line of Credit Promissory Note dated June 12, 1998, a certain Third
Amendment to Line of Credit Promissory Note dated August 31, 1999, and a certain
Fourth Amendment to Line of Credit Promissory Note of even date herewith
(collectively, the "Note").

     C.  The repayment of the indebtedness evidenced by the Note is secured by a
Security Agreement dated October 25, 1995 between Borrower and Bank, as amended
by a First Amendment to Security Agreement dated June 12, 1998 and a Second
Amendment to Security Agreement dated August 31, 1999 (the "Security
Agreement").  The repayment of the Note is further secured by that certain
Patent Security Agreement and that certain Trademark Security Agreement of even
date herewith from Borrower to Bank.

     D.  The Borrower has violated certain covenants set forth in the Agreement
and has requested that the Bank waive such violations, and the Bank has agreed,
subject to the terms and conditions hereinafter described.

                                   WITNESSETH
                                   ----------

     NOW, THEREFORE, in consideration of the premises and the mutual covenants
set forth herein, and other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties hereby agree that the
Agreement is hereby modified and amended as follows (the Agreement, as amended,
is hereinafter referred to as the "Agreement"):
<PAGE>

     1.  Recitals.  The parties acknowledge and agree that the foregoing
         --------
Recitals are true and correct, and are incorporated herein by reference.

     2.  Amendments to Agreement.
         -----------------------

         A.  The Bank hereby agrees that Borrower shall not be required to
comply with the requirement set forth in Section 6.05, which requires the
Borrower to maintain a minimum Tangible Net Worth of Six Million Five Hundred
Thousand Dollars ($6,500,000.00), until March 31, 2001. Effective as of April,
2001 and at all times thereafter, Borrower shall be required to maintain a
minimum Tangible Net Worth of at least Six Million Five Hundred Thousand Dollars
($6,500,000.00), which shall be reviewed quarterly by the Bank. For purposes
hereof, the Borrower's net worth shall be determined at the end of each calendar
quarter, based on the audited financial statements or the 10-Q financial reports
of the Borrower.

         B.  Notwithstanding the provisions set forth in Section 2(K) of the
Fourth Amendment to Revolving Credit and Letter of Credit Agreement, the Bank
agrees that the net operating loss sustained by the Borrower for the fiscal year
ending March 31, 2000 shall not constitute a default under the Agreement. For
each fiscal year ending after March 31, 2000, it shall constitute a default
under the Agreement if Borrower experiences a net operating loss, as determined
by the Bank based upon the audited annual financial statements of the Borrower.

         C.  Borrower agrees it shall constitute a default under the Agreement
if the Borrower experiences at any time an aggregate year-to-date loss (before
income taxes) in excess of One Million Dollars ($1,000,000.00), beginning with
the quarter ending June 30, 2000.

         D.  The principal amount of all Advances under the Line of Credit shall
bear interest at a fluctuating rate equal to the Bank's Prime Rate plus one-half
of one (0.5) percentage point per annum, until such time as the Borrower's
Tangible Net Worth is equal to or greater than Six Million Five Hundred Thousand
Dollars ($6,500,000.00). At all times thereafter during which the Borrower's
Tangible Net Worth is equal to or greater than $6,500,000.00, all Advances under
the line of credit shall bear interest at a fluctuating rate equal to the Bank's
Prime Rate, as announced from time to time.

         E.  The definition of "Note" on Page 3 of the Agreement is hereby
modified to mean the Line of Credit Promissory Note, as heretofore amended and
as amended on even date herewith.

         F.  The definition of "Other Agreements" on Page 4 of the Agreement is
hereby modified to include this Fifth Amendment, the Fourth Amendment to Line of
Credit Promissory Note, and the Patent Security Agreement and the Trademark
Security Agreement of even date herewith between the Borrower and Bank.

     3.  Representations and Warranties.  The Borrower hereby confirms that all
         ------------------------------
of the representations and warranties set forth in Section IV of the Agreement
are accurate, complete and correct as of the date of this Fifth Amendment, and
are incorporated herein by reference.

                                       2
<PAGE>

     4.  Waiver and Release.  The Borrower hereby represents and warrants that
         ------------------
no event of default has occurred under the Loan Documents.  The Borrower
acknowledges and agrees that it has no right of set-off or defense of any kind
against the Bank with respect to the repayment of the Note or the enforcement or
validity of any of the Other Agreements, and to the extent any such right of
set-off or defense existed, such rights are hereby waived and forever released.
The Borrower does hereby release and forever discharge the Bank, its officers,
employees and agents from any and all claims of every kind and nature, in law or
in equity, that the Borrower may have had or now has to the best of its
knowledge, for any matter arising prior to the date hereof.

     5.  Effect of Amendment.  Except as modified and amended herein, the
         -------------------
Agreement shall be and remain in full force and effect.  In the event of any
conflict between the terms and provisions of the Agreement and this Fifth
Amendment, the terms and provisions of this Fifth Amendment shall prevail.
Nothing contained herein shall constitute a novation under the Note.

     IN WITNESS WHEREOF, the parties hereto have caused this Fifth Amendment to
be executed under seal, intending this to be a sealed instrument, as of the date
first above written.

WITNESS/ATTEST:                  ENVIRONMENTAL ELEMENTS CORPORATION

                                 By: /s/
----------------------------            -----------------------------(SEAL)
                                        James B. Sinclair,
                                        Vice-President and
                                        Chief Financial Officer

                                 MERCANTILE-SAFE DEPOSIT AND TRUST COMPANY

                                 By: /s/
----------------------------            -----------------------------(SEAL)
                                        Philip G. Enstice,
                                        Senior Vice-President

                                       3<PAGE>

                                                                   EXHIBIT 10.3

                           PATENT SECURITY AGREEMENT
                           -------------------------

          THIS PATENT SECURITY AGREEMENT (the "Agreement") is made and entered
into as of June 30, 2000, by ENVIRONMENTAL ELEMENTS CORPORATION, a Delaware
corporation (the "Debtor"), in favor of MERCANTILE-SAFE DEPOSIT AND TRUST
COMPANY, a Maryland banking corporation (the "Secured Party").

                                    Recitals
                                    --------

          A.  The Secured Party and the Debtor are parties to that certain
Revolving Credit and Letter of Credit Agreement dated as of November 24, 1993
(as amended, supplemented, or otherwise modified, the "Agreement"). Capitalized
terms used herein without definition have the meanings provided in the
Agreement.

          B.  To secure the Obligations (the "Obligations"), the Debtor has
agreed to enter into this Agreement.

                                   Agreement
                                   ---------

          NOW THEREFORE, in consideration of the premises and in order to induce
the Secured Party to enter into the Lease, the Debtor hereby agrees with the
Secured Party as follows:

          1.  Creation of Security Interest. In order to secure the payment of
              -----------------------------
and performance of all Obligations, the Debtor hereby grants to the Secured
Party a security interest in and assigns to Secured Party all of the Debtor's
patents and patent applications now owned or licensed by the Debtor in the
United States, Canada, China and United Kingdom (the "Patent Countries"),
including but not limited to the patents and patent applications listed on
Schedule A attached hereto and made a part hereof, and the inventions and
----------
improvements described and claimed therein, and (i) all reissues, divisions,
continuations, renewals, extensions and continuations in part of any of the
foregoing, (ii) all income, royalties, damages and payments now and hereafter
due or payable with respect thereto, including, without limitation, payments
under all licenses entered into in connection therewith and damages and payments
for past or future infringements thereof, (ii) the right to sue for past,
present and future infringements thereof, and (iii) all rights corresponding
thereto throughout the world (all of the foregoing patents and patent
applications, together with the items described in clauses (i)-(iii) above, are
referred to herein, either individually or collectively, as the "Patents").  All
of the foregoing shall be the "Collateral".

          2.  Restrictions on Future Agreements.  Until the Obligations shall
              ---------------------------------
have been satisfied in full, the Debtor will not without the Secured Party's
prior written consent, (a) enter into any agreement that is inconsistent with
the Debtor's obligations under this Agreement or any Other Agreements to which
the Debtor is a party, (b) intentionally take any action, or permit any action
to be taken by others subject to its control, or intentionally fail to take any
action (including, without limitation, the intentional abandonment of any Patent
that is material to the
<PAGE>

conduct of the Debtor's business as then conducted), that would adversely affect
the validity or enforceability of the rights transferred to the Secured Party
under this Agreement, or (c) enter into any other contractual obligations that
would restrict or inhibit the Secured Party's rights to sell or otherwise
dispose of the Patents or any part thereof after the occurrence of any Lease
Event of Default; provided, however, that the Debtor may, without the Secured
Party's consent, grant one or more nonexclusive, transferable licenses under the
Patents, provided that (i) each such license is subject to the terms of this
Agreement, (ii) that such license is not otherwise inconsistent with the
Debtor's obligations under this Agreement, or any Other Agreements to which the
Debtor is a party and (iii) the Debtor shall give the Secured Party prior
written notice of such grant; provided further, that promptly, but no later than
five (5) business days after the receipt of any proceeds resulting from such
assignment or exclusive license, the Debtor shall pay such proceeds to the
Secured Party.

          3.  Patents. The Debtor represents and warrants that, to the best of
              -------
its knowledge, it has provided to Secured Party a list of all of the Debtor's
unexpired patents and patent applications, wherever located, that are as of the
date hereof used by the Debtor in its business or owned by or are pending on
behalf of the Debtor.

          4.  Representations and Warranties. The Debtor hereby represents,
              ------------------------------
warrants, covenants and agrees that:

              (a) It is the owner or authorized licensee of all of the right,
title and interest in the Patents, free from any lien or encumbrance except for
the security interest granted pursuant to this Agreement (other than Permitted
Encumbrances).

              (b) It has made no previous assignment, transfer or agreements in
conflict herewith or constituting a present or future assignment, transfer, or
encumbrance on any of the Patents.

              (c) After the date hereof and prior to termination of this
Agreement pursuant to Section 5, it will not execute, and there will not be on
file in any public office, any financing statement or other document or
instruments evidencing or giving notice of liens affecting the Patents.

              (d) To its knowledge, no material infringement or unauthorized use
presently is being made of any of the Patents that would adversely affect the
fair market value of the Patents or the benefits of this Agreement granted to
the Secured Party, including, without limitation, the remedies of the Secured
Party hereunder.

              (e) There has been no judgment holding any of the Patents invalid
or unenforceable, in whole or part nor is the validity or enforceability of any
of the Patents presently being questioned in any litigation or proceeding to
which the Debtor is a party.

          5.  Term. The term of the Agreement shall commence as of the date
              ----
hereof and terminate at such time as all of the Obligations have been fully
satisfied and Borrower has no remaining loan or other credit facilities of any
kind with the Secured Party.

                                       2
<PAGE>

          6.  Duties of the Debtor. Until all Obligations then due and owing
              --------------------
shall have been paid in full and this Agreement shall have been terminated, the
Debtor shall (i) prosecute diligently any patent application that is part of the
Patents pending as of the date hereof, (ii) make application on unpatented but
patentable inventions that are part of the Collateral as it deems appropriate in
its business judgment, (iii) preserve and maintain all rights in patent
applications and patents that are part of the Patents, including the payment of
all maintenance fees; (iv) not intentionally abandon any pending patent
application if in its business judgment the value thereof could be expected to
justify the cost of obtaining such patent, and (v) not intentionally abandon any
Patent. Any expenses incurred in connection with the applications referred to in
this Section 6 shall be borne by the Debtor. The Debtor agrees to retain or
employ an experienced patent attorney for the filing and prosecution of all such
applications and other proceedings. The Debtor shall keep the Secured Party
advised on a current basis of the abandonment of any Patent or Patent
application, and the grant of any nonexclusive patent license, to the extent
such Patents or patent applications are part of the Patents.

          If the Debtor fails to comply with any of the foregoing duties, the
Secured Party may so comply in the Debtor's name to the extent permitted by law,
but at the Debtor's expense, and the Debtor hereby agrees to reimburse the
Secured Party in full for all reasonable expenses, including the reasonable fees
and disbursements of attorneys and paralegals (excluding charges for inside
counsel) incurred by the Secured Party in protecting, defending and maintaining
the Patents.

          If the Debtor shall fail to pay when due any fees required to be paid
by it hereunder, or shall fail to discharge any Lien prohibited hereby, or shall
fail to comply with any other duty hereunder, the Secured Party may, but shall
not be required to, pay, satisfy, discharge or bond the same for the account of
the Debtor, and all moneys so paid out shall be a part of the  Obligations of
the Debtor repayable on demand, together with interest at the default rate.

          The Debtor shall take all action reasonably necessary to preserve and
maintain the validity, perfection and priority of the Secured Party's interest
granted herein in the Patents, subject to Permitted Encumbrances.

          7.  Secured Party's Right to Sue.  From and after the occurrence and
              ----------------------------
during the continuance of an Event of Default, the Secured Party shall have the
right, but shall in no way be obligated, to bring suit in its own name to
enforce the Patents, and any licenses thereunder, and, if the Secured Party
shall commence any such suit, the Debtor shall, at the request of the Secured
Party, do any and all lawful acts and execute any and all proper documents
reasonably required by the Secured Party in aid of such enforcement and the
Debtor shall indemnify and shall, upon demand, promptly reimburse the Secured
Party for all damages and reasonable costs and expenses, including reasonable
attorneys' fees and expenses, incurred by the Secured Party in the exercise of
its rights under this Section 7.

          8.  Waivers. No course of dealing between the Debtor and the Secured
              -------
Party, nor any failure to exercise, nor any delay in exercising, on the part of
the Secured Party, any right, power or privilege hereunder shall operate as a
waiver thereof; nor shall any single or

                                       3
<PAGE>

partial exercise of any right, power or privilege hereunder or thereunder
preclude any other or further exercise thereof or the exercise of any other
right, power or privilege.

          9.  Amendments. This Agreement or any provision thereof may be
              ----------
changed, waived, or terminated only by a writing executed by the parties hereto.

          10. Remedies.  If any Event of Default shall have occurred and be
              --------
continuing, the Secured Party shall be entitled to exercise in respect of the
Patents, in addition to other rights and remedies provided for herein, and in
the Other Agreements or otherwise available to it, all of the rights and
remedies of a secured party under the Uniform Commercial Code in effect in the
State of Maryland ("UCC"), whether or not the UCC applies to the Patents, and
also may (i) require the Debtor, and the Debtor hereby agrees that it will upon
written the request of the Secured Party, forthwith, (A) execute and deliver an
assignment, in the form required by Secured Party, of all right, title and
interest in and to the Patents, and (B) take such other action as the Secured
Party may request to effectuate the outright assignment of such Patents or to
exercise, register or further perfect and protect its rights and remedies with
respect to such assigned Patents, and (ii) without notice except as specified
below, sell the Patents or any part thereof in one or more parcels at public or
private sale, at any of the Secured Party's offices or elsewhere, for cash, on
credit or for future delivery, and upon such terms as the Secured Party may deem
commercially reasonable.  The Debtor agrees that at least ten (10) days' notice
to the Debtor of the time and place of any public sale or the time that any
private sale is to be made shall constitute reasonable notification.  The
Secured Party shall not be obligated to make any sale of the Patents regardless
of notice of sale having been given. The Secured Party may adjourn any public or
private sale from time to time by announcement at the time and place fixed
therefor, and such sale may, without further notice, be made at the time and
place to which it was so adjourned.  The Secured Party may purchase all or any
part of the Patents at public or, if permitted by law, private sale and, in lieu
of actual payment of such purchase price, may setoff the amount of such price
against the Obligations.  The proceeds realized from the sale of any Patents
shall be applied as provided in the Agreement. If any deficiency shall arise,
the Debtor shall remain liable to the Secured Party therefor.  The commencement
of any action, legal or equitable, or the rendering of any judgment or decree
for deficiency shall not affect the Secured Party's interest in the Patents
until the Obligations are fully paid.  The Debtor agrees that the Secured Party
has no obligation to preserve rights to the Patents against any other parties.

          11. Cumulative Remedies; Power of Attorney.  All of the Secured
              --------------------------------------
Party's rights and remedies with respect to the Patents, whether established
hereby, by the Lease, by any other Loan Document, or by law shall be cumulative
and may be exercised singularly or concurrently.  The Debtor hereby authorizes
the Secured Party to make, constitute and appoint any officer or agent of the
Secured Party as the Secured Party may select, in its sole discretion, as the
Debtor's true and lawful attorney-in-fact, with power, from and after the
occurrence of an Event of Default to (a) endorse the Debtor's name on all
applications, documents, papers and instruments necessary or desirable for the
Secured Party in the use of the Patents, including, without limitation, if the
Debtor fails to execute and deliver within three (3) days of the Secured Party's
written request therefor the assignment required by Secured Party, (b) take any
other actions with respect to the Patents as the Secured Party deems in the best
interest of the Secured

                                       4
<PAGE>

Party, (c) grant or issue any exclusive or non-exclusive license under the
Patents to anyone, or (d) assign, pledge, convey or otherwise transfer title in
or dispose of the Patents to anyone. The Debtor hereby ratifies all that such
attorney shall lawfully do or cause to be done by virtue hereof in accordance
with the terms hereof. This power of attorney, being coupled with an interest,
shall be irrevocable until all Obligations shall have been paid in full and this
Agreement has been terminated. The Debtor acknowledges and agrees that this
Agreement is not intended to limit or restrict in any way the rights and
remedies of the Secured Party under the Lease and the Other Agreements but
rather is intended to facilitate the exercise of such rights and remedies.

          12. Notice. Any notice, approval, consent or other communication to
              ------
any party hereunder shall be in the form and manner, and to the addresses as set
forth in the Agreement.

          13. Continuing Security Interest; Binding Effect; Benefits of
              ---------------------------------------------------------
Agreement. This Agreement shall create a continuing security interest in the
---------
Patents and shall (i) remain in full force and effect until payment in full of
all Obligations, (ii) be binding upon the Debtor its successors and assigns, and
(iii) inure, together with the rights and remedies of the Secured Party
hereunder, to the benefit of the Secured Party and its successors and permitted,
transferees and assigns.

          14. Authority of Secured Party. The Secured Party shall have and be
              --------------------------
entitled to exercise all powers hereunder that are specifically delegated to the
Secured Party by the terms hereof, together with such powers as are reasonably
incident thereto. The Secured Party may perform any of its duties hereunder or
in connection with the Patents by or through agents or employees and shall be
entitled to retain counsel and to act in reliance upon the advice of counsel
concerning all such matters. The Secured Party and its directors, officers,
employees, attorneys and agents shall be entitled to rely on any communication,
instrument or document believed by it or them to be genuine and correct and to
have been signed or sent by the proper person or persons. Neither the Secured
Party nor any director, officer, employee, attorney or agent of the Secured
Party shall be liable to the Debtor for any action taken or omitted to be taken
by it or them hereunder, except for its or their own gross negligence, willful
misconduct, nor shall the Secured Party be responsible for the validity,
effectiveness or sufficiency hereof or of any document or security furnished
pursuant hereto. The Debtor agrees to indemnify and hold harmless the Secured
Party and any other person from and against any and all reasonable costs and
expenses (including reasonable attorney's fees and expenses), claims or
liability incurred by the Secured Party or such person hereunder, unless such
claim or liability shall be due to willful misconduct or gross negligence on the
part of the Secured Party or such person.

          15. Waiver. To the fullest extent it may lawfully so agree, the
              ------
Debtor agrees that it will not at any time insist upon, claim, plead, or take
any benefit or advantage of any appraisement, valuation, stay, extension,
moratorium, redemption or similar law now or hereafter in force in order to
prevent, delay, or hinder the enforcement hereof or the absolute sale of any
part of the Patents. The Debtor for itself and all who claim through it, so far
as it or they now or hereafter lawfully may do so, hereby waives the benefit of
all such laws, and all right to have the Patents marshalled upon any foreclosure
hereof, and agrees that any court having jurisdiction to foreclose this
Agreement may order the sale of the Patents as an entirety.

                                       5
<PAGE>

          16. [Intentionally Omitted].

          17. Reinstatement. This Agreement shall continue to be effective or
              -------------
be reinstated, as the case may be, if at any time any amount received by the
Secured Party in respect of the Obligations is rescinded or must otherwise be
restored or returned by the Secured Party upon the insolvency, bankruptcy,
dissolution, liquidation or reorganization of the Debtor or upon the appointment
of any intervenor or conservator of, or trustee or similar official for, the
Debtor or any substantial part of its assets, or otherwise, all as though such
payments had not been made.

          18. GOVERNING LAW; SUBMISSION TO JURISDICTION WAIVER OF JURY TRIAL:
              ---------------------------------------------------------------
WAIVER OF DAMAGES. (a) THIS AGREEMENT SHALL BE GOVERNED BY AND INTERPRETED UNDER
-----------------
THE INTERNAL LAWS (AS OPPOSED TO CONFLICT OF LAWS PROVISIONS) AND DECISIONS OF
THE STATE OF MARYLAND, AND ANY DISPUTE ARISING OUT OF, CONNECTED WITH, RELATED
TO, OR INCIDENTAL TO THE RELATIONSHIP ESTABLISHED BETWEEN THE DEBTOR AND THE
SECURED PARTY IN CONNECTION WITH THIS AGREEMENT, AND WHETHER ARISING IN
CONTRACT, TORT, EQUITY OR OTHERWISE, SHALL BE RESOLVED IN ACCORDANCE WITH THE
INTERNAL LAWS (AS OPPOSED TO THE CONFLICTS OF LAWS PROVISIONS) AND DECISIONS OF
THE STATE OF MARYLAND.

              (a) EXCEPT AS PROVIDED IN THE NEXT PARAGRAPH, THE DEBTOR AND THE
SECURED PARTY AGREE THAT ALL DISPUTES BETWEEN THEM ARISING OUT OF, CONNECTED
WITH, RELATED TO, OR INCIDENTAL TO THE RELATIONSHIP ESTABLISHED BETWEEN THEM IN
CONNECTION WITH THIS AGREEMENT, AND WHETHER ARISING IN CONTRACT, TORT, EQUITY,
OR OTHERWISE, SHALL BE RESOLVED ONLY BY STATE OR FEDERAL COURTS LOCATED IN
MARYLAND, BUT THE DEBTOR AND THE SECURED PARTY ACKNOWLEDGE THAT ANY APPEALS FROM
THOSE COURTS MAY HAVE TO BE HEARD BY A FEDERAL COURT LOCATED OUTSIDE OF
MARYLAND. THE DEBTOR WAIVES IN ALL DISPUTES ANY OBJECTION THAT IT MAY HAVE TO
THE LOCATION OF THE COURT CONSIDERING THE DISPUTE INCLUDING, WITHOUT LIMITATION,
ANY OBJECTION TO THE LAYING OF VENUE OR BASED ON THE GROUNDS OF FORUM NON
CONVENIENS.

              (b) THE DEBTOR AGREES THAT THE SECURED PARTY SHALL HAVE THE RIGHT,
TO THE EXTENT PERMITTED BY APPLICABLE LAW, TO PROCEED AGAINST THE DEBTOR OR THE
PATENTS IN A COURT IN ANY LOCATION REASONABLY SELECTED IN GOOD FAITH TO ENABLE
THE SECURED PARTY TO REALIZE ON THE PATENTS, OR TO ENFORCE A JUDGMENT OR OTHER
COURT ORDER ENTERED IN FAVOR OF THE SECURED PARTY. THE DEBTOR AGREES THAT IT
WILL NOT ASSERT ANY PERMISSIVE COUNTERCLAIMS, SETOFFS OR CROSS CLAIMS IN ANY
PROCEEDING BROUGHT BY THE SECURED PARTY TO REALIZE ON THE PATENTS, OR TO ENFORCE
A JUDGMENT OR OTHER COURT ORDER IN FAVOR OF THE SECURED PARTY. THE DEBTOR WAIVES
ANY OBJECTION THAT IT MAY HAVE TO THE LOCATION OF THE COURT IN WHICH THE

                                       6
<PAGE>

SECURED PARTY HAS COMMENCED A PROCEEDING DESCRIBED IN THIS PARAGRAPH INCLUDING,
WITHOUT LIMITATION, ANY OBJECTION TO THE LAYING OF VENUE OR BASED ON THE GROUNDS
OF FORUM NON CONVENIENS.

              (c) THE DEBTOR AND THE SECURED PARTY EACH WAIVE ANY RIGHT TO HAVE
A JURY PARTICIPATE IN RESOLVING ANY DISPUTE, WHETHER SOUNDING IN CONTRACT, TORT,
OR OTHERWISE ARISING OUT OF, CONNECTED WITH, RELATED TO OR INCIDENTAL TO THE
RELATIONSHIP ESTABLISHED BETWEEN THEM IN CONNECTION WITH THIS AGREEMENT.
INSTEAD, ANY DISPUTES RESOLVED IN COURT WILL BE RESOLVED IN A BENCH TRIAL
WITHOUT A JURY.

              (d) THE DEBTOR (I) AGREES THAT THE SECURED PARTY SHALL NOT HAVE
ANY LIABILITY TO THE DEBTOR (WHETHER SOUNDING IN TORT, CONTRACT OR OTHERWISE)
FOR LOSSES SUFFERED BY THE DEBTOR IN CONNECTION WITH, ARISING OUT OF, OR IN ANY
WAY RELATED TO, THE TRANSACTIONS CONTEMPLATED AND THE RELATIONSHIP ESTABLISHED
BY THIS AGREEMENT, OR ANY ACT, OMISSION OR EVENT OCCURRING IN CONNECTION
THEREWITH, UNLESS IT IS DETERMINED BY A JUDGMENT OF A COURT THAT IS BINDING ON
THE SECURED PARTY (WHICH JUDGMENT SHALL BE FINAL AND NOT SUBJECT TO REVIEW ON
APPEAL), THAT SUCH LOSSES WERE THE RESULT OF ACTS OR OMISSIONS ON THE PART OF
THE SECURED PARTY, CONSTITUTING GROSS NEGLIGENCE OR WILLFUL MISCONDUCT AND (II)
WAIVES, RELEASES AND AGREES NOT TO SUE UPON ANY CLAIM AGAINST THE SECURED PARTY
(WHETHER SOUNDING IN TORT, CONTRACT OR OTHERWISE), EXCEPT A CLAIM BASED UPON
GROSS NEGLIGENCE OR WILLFUL MISCONDUCT. WHETHER OR NOT SUCH DAMAGES ARE RELATED
TO A CLAIM THAT IS SUBJECT TO THE WAIVER EFFECTED ABOVE AND WHETHER OR NOT SUCH
WAIVER IS EFFECTIVE, THE SECURED PARTY SHALL NOT HAVE ANY LIABILITY WITH RESPECT
TO ANY CLAIM FOR, ANY SPECIAL, INDIRECT, CONSEQUENTIAL OR PUNITIVE DAMAGES
SUFFERED BY THE DEBTOR IN CONNECTION WITH, ARISING OUT OF, OR IN ANY WAY RELATED
TO THE TRANSACTIONS CONTEMPLATED OR THE RELATIONSHIP ESTABLISHED BY THIS
AGREEMENT, OR ANY ACT, OMISSION OR EVENT OCCURRING IN CONNECTION THEREWITH.
UNLESS IT IS DETERMINED BY A JUDGMENT OF A COURT THAT IS BINDING ON THE SECURED
PARTY (WHICH JUDGMENT SHALL BE FINAL AND NOT SUBJECT TO REVIEW ON APPEAL), THAT
SUCH DAMAGES WERE THE RESULT OF ACTS OR OMISSIONS ON THE PART OF THE SECURED
PARTY, CONSTITUTING GROSS NEGLIGENCE OR WILLFUL MISCONDUCT.

              (e) THE DEBTOR WAIVES ALL RIGHTS OF NOTICE AND HEARING OF ANY KIND
PRIOR TO THE EXERCISE BY THE SECURED PARTY OF ITS RIGHTS FROM AND AFTER THE
OCCURRENCE OF AN EVENT OF DEFAULT TO REPOSSESS THE PATENTS WITH JUDICIAL PROCESS
OR TO REPLEVY, ATTACH OR LEVY UPON THE PATENTS OR OTHER SECURITY FOR THE
OBLIGATIONS. THE

                                       7
<PAGE>

DEBTOR WAIVES THE POSTING OF ANY BOND OTHERWISE REQUIRED OF THE SECURED PARTY IN
CONNECTION WITH ANY JUDICIAL PROCESS OR PROCEEDING TO OBTAIN POSSESSION OF,
REPLEVY, ATTACH OR LEVY UPON PATENTS OR OTHER SECURITY FOR THE OBLIGATIONS, TO
ENFORCE ANY JUDGMENT OR OTHER COURT ORDER ENTERED IN FAVOR OF THE SECURED PARTY,
OR TO ENFORCE BY SPECIFIC PERFORMANCE, TEMPORARY RESTRAINING ORDER, PRELIMINARY
OR PERMANENT INJUNCTION THIS AGREEMENT OR ANY OTHER AGREEMENT OR DOCUMENT
BETWEEN THE DEBTOR AND THE SECURED PARTY.

          IN WITNESS WHEREOF, the Debtor has duly executed and delivered this
Agreement under seal as of the day and year first above written.

                                  ENVIRONMENTAL ELEMENTS CORPORATION

                                  By: /s/
                                      ----------------------------------
                                      James B. Sinclair, Vice-President
                                      and Chief Financial Officer

                        CERTIFICATE OF ACKNOWLEDGEMENT

STATE OF MARYLAND             :
                              :
CITY/COUNTY OF _______________:

          Before me, the undersigned, a Notary Public in and for the State
aforesaid, on this 30th day of June, 2000, personally appeared JAMES B.
SINCLAIR, to me known personally or proven to be the Vice-President and Chief
Financial Officer of Environmental Elements Corporation, a Delaware corporation,
and who deposes that said instrument was signed and sealed on behalf of said
Corporation by authority of its Board of Directors, and said JAMES B. SINCLAIR
acknowledged said instrument to be the free act and deed of said Corporation.

                                      ----------------------------------
                                      Notary Public
                                      My commission expires:
                                                            ------------
                                       8
<PAGE>

                                 SCHEDULE A TO
                                 ----------
                           PATENT SECURITY AGREEMENT
                                 U.S. PATENTS

<TABLE>
<CAPTION>
       Serial Number or
     Registration Number                               Title                         Docket No.
<C>                           <S>                                                    <C>
          4,481,172           Process for Removal of Sulphur Oxides from Waste        MR717-2
                              Gases
          4,597,782           Filter Bag Tensioning System and Method                 MR717-15
          4,655,804           Hopper Gas Distribution System                          MR717-19
          4,615,505           Fluid Valve System                                      MR717-23
          4,609,009           Stepped Plenum System                                   MR717-32
          4,377,557           Process for Removal of Sulfur Oxides from Waste Gases   MR717-41
          4,385,039           Process for Removal of Sulfur Oxides from Waste Gases   MR717-43
          4,811,197           Electrostatic Dust Collection System                    MR717-47
          4,895,491           Fan Blade Protection System                             MR717-48
          5,229,077           Sulfur Rate Control System                              MR717-60
          5,311,420           Automatic Back Corona Detection & Protection System     MR717-68
          5,707,428           Laminar Flow Electrostatic Precipitation System         MR717-83
          5,695,549           System for Removing Fine Particulates from a Gas        MR717-84
                              Stream
          5,785,932           Catalytic Reactor for Oxidizing Mercury Vapor           MR717-85
          5,733,360           Corona Discharge Reactor                                MR717-87
          5,626,652           Laminar Flow Electrostatic Precipitator having a        MR717-92
                              Moving Electrode
          5,759,240           Laminar Flow Electrostatic Precipitator with            MR717-93
                              Sandwich Structure Electrodes
          5,725,638           Modular Electrostatic Precipitation Dust Collection     MR717-94
                              Plate Assembly
         09/132,311           Electrostatic Precipitator Rapper Controller System     MR717-96
          4,373,936           Filter Bag Tensioning Device and Method                 MR717-98
         09/273,350           Air Filter with combined Enhanced Collection            MR717-101
                              Efficiency and Surface Sterilization
</TABLE>

                                      A-1
<PAGE>

                                 SCHEDULE A TO
                                 ----------
                           PATENT SECURITY AGREEMENT
                               CANADIAN PATENTS

<TABLE>
<CAPTION>
       Serial Number or
     Registration Number                               Title                               Docket No.
<C>                           <S>                                                     <C>
         08/512,198           Laminar Flow Electrostatic Precipitation System         MR717-83/CA
          1,277,255           Stepped Plenum System                                   PAT 9576-1 (Borden
                                                                                      Ladner Gervais Scott
                                                                                      & Aylen)
              80H27           Filter Bag Tensioning Device and Method                 Pat # 1,178,218
                                                                                      (Scott & Aylen)
</TABLE>
<PAGE>

                                 SCHEDULE A TO
                                 ----------
                           PATENT SECURITY AGREEMENT
                                CHINESE PATENTS

<TABLE>
<CAPTION>
       Serial Number or
     Registration Number                               Title                           Docket No.
<C>                           <S>                                                     <C>
         08/512,198           Laminar Flow Electrostatic Precipitation System         MR717-83/CN
</TABLE>
<PAGE>

                                 SCHEDULE A TO
                                 ----------
                           PATENT SECURITY AGREEMENT
                             UNITED KINGDOM PATENTS

<TABLE>
<CAPTION>
       Serial Number or
     Registration Number                               Title                               Docket No.
<C>                           <S>                                                     <C>
             80H27D           Improved Method for Filter Bag Tensioning Device        Pat # 2133310
                                                                                      (8334515) (Haseltine
                                                                                      Lake Partners)
              80H27           Filter Bag Tensioning Device and Method                 Pat # 2081127
                                                                                      (8123229) Hasteltine
                                                                                      Lake Partners)
</TABLE>

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00013-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00013-of-00352.parquet"}]]