<PAGE>
                                                                    EXHIBIT 10.1
                                                                 Fifth Amendment

                        FIFTH AMENDMENT TO LOAN AGREEMENT

         THIS FIFTH AMENDMENT (this "Amendment") is made as of this 9th day of
December, 2002, by and among SystemOne Technologies Inc. (f/k/a Mansur
Industries Inc.), a Florida corporation (the "Borrower"), Hanseatic Americas LDC
("Hanseatic"), Environmental Opportunities Fund II, LP ("Environmental II") and
Environmental Opportunities Fund II (Institutional), LP ("Environmental
Institutional", and collectively with Hanseatic and Environmental II, the
"Lenders").

                                    RECITALS

         WHEREAS, the Borrower and the Lenders are parties to that certain Loan
Agreement dated August 7, 2000, as amended by a First Amendment to Loan
Agreement dated as of November 10, 2000, a Second Amendment to Loan Agreement
dated as of November 30, 2000, a Third Amendment to Loan Agreement dated as of
February 27, 2002 and a Fourth Amendment to Loan Agreement dated as of September
30, 2002 (as amended, the "Loan Agreement") and in connection therewith the
Borrower issued to the Lenders promissory notes in the aggregate principal
amount of $3,300,000 (the "Outstanding Notes") and warrants exercisable for in
the aggregate 942,858 shares of the Borrower's common stock, $.001 par value;
and

         WHEREAS, as part of the recapitalization of the Borrower and pursuant
to the Exchange Agreement (the "Exchange Agreement"), dated December 9, 2002, by
and among the Borrower, the Lenders and the additional parties thereto, the
Borrower and the Lenders desire to cancel the Outstanding Notes and amend the
Loan Agreement and Loan Documents (as defined in the Loan Agreement) to (i)
increase the principal amount outstanding thereunder to include the interest
accrued from, respectively, the Closing Date and the Supplemental Closing Date
(each as defined in the Loan Agreement) to the date hereof, (ii) change the
Maturity Date (as defined in the Loan Agreement) from September 30, 2002 to
December 31, 2005, (iii) change the interest rate from sixteen percent (16%) per
annum to ten percent (10%) per annum, and (iv) issue new promissory notes (the
"New Notes"), all according to the terms of the Loan Agreement as amended by
this Amendment;

         NOW, THEREFORE, in consideration of the premises and for other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties hereto agree as follows:

         1.       Article I, Section 1.1 (xxxvi) of the Loan Agreement is hereby
amended by deleting Article I, Section 1.1 (xxxvi) in its entirety and
substituting therefor a new Article I, Section 1.1 (xxxvi) to read as follows:

                  (xxxvi) The term "Maturity Date" shall mean December 31, 2005.

         2.       Article I, Section 1.1 (xxxviii) of the Loan Agreement is
hereby amended by deleting Article I, Section 1.1 (xxxviii) in its entirety and
substituting therefor a new Article I, Section 1.1 (xxxviii) to read as follows:
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                  (xxxviii) The term "Notes" shall mean those notes, each in the
         form attached hereto as Exhibit A dated as of the Closing Date,
         executed by the Borrower, as the maker, and delivered to each Lender,
         as payee, in the aggregate principal amount of $4,418,373, which Notes,
         collectively, evidence the Loan under this Agreement.

         3.       Article I, Section 1.1 (xxxxviii) of the Loan Agreement is
hereby amended by deleting Article I, Section 1.1 (xxxxviii) in its entirety and
substituting therefor a new Article I, Section 1.1 (xxxxviii) to read as
follows:

                  (xxxxviii) The term "Security Agreement" shall mean that
         certain Security Agreement in the form attached hereto as Exhibit C,
         dated the Closing Date, and amended by that certain First Amendment
         dated November 10, 2000, that certain Second Amendment dated November
         30, 2000 and that certain Third Amendment dated December 9, 2002, as
         from time to time further amended, whereby the Borrower has pledged,
         assigned, hypothecated, conveyed, transferred, given and granted to the
         Lenders, and each of them, a continuing pledge, of and security
         interest in all of the security described therein.

         4.       Article I, Section 1.1 (lviii) of the Loan Agreement is hereby
amended by deleting Article I, Section 1.1 (lviii) in its entirety and
substituting therefor a new Article I, Section 1.1 (lviii) to read as follows:

                  (lviii) The term "Outstanding Notes" shall mean the Borrower's
         promissory notes in the aggregate principal amount of $3,300,000 issued
         pursuant to this Agreement to the Lenders, respectively, on the
         Supplemental Closing Date.

         5.       The following new section is hereby added immediately
following the definition of "Supplemental Closing Date" under Article I (which,
together with the preceding clause (lviv) shall be re-designated, respectively,
clause (lix) and clause (lx) thereof):

                  (lxi) The term "Second Supplemental Closing Date" shall mean
December 9, 2002.

         6.       Article II, Section 2.2 of the Loan Agreement is hereby
amended by deleting Article II, Section 2.2 in its entirety and substituting
therefor a new Article II, Section 2.2 to read as follows:

                  Section 2.2 Notes. The obligation of the Borrower to repay all
         monies advanced by the Lenders, and each of them, to the Borrower in
         connection with the Loan shall be evidenced by the Notes, each in the
         form of Exhibit A annexed hereto. On the Second Supplemental Closing
         Date, the Borrower shall have duly executed and delivered to each
         Lender, in substitution for the Outstanding Note held thereby, a Note,
         which shall (i) be dated as of the Second Supplemental Closing Date,
         (ii) be registered in the name of the Lender to whom issued, (iii)

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         have a principal sum equal to the aggregate amounts advanced by such
         Lender to the Borrower plus all interest accrued from the Closing Date
         through the Second Supplemental Closing Date, which shall be payable in
         the amounts and on the dates provided for in Section 2.4 hereof and
         (iv) bear interest at the rates payable on the dates and in the manner
         provided for in Section 2.3 hereof.

         7.       Article II, Section 2.3 of the Loan Agreement is hereby
amended by deleting Article II, Section 2.3 in its entirety and substituting
therefor a new Article II, Section 2.3 to read as follows:

                  Section 2.3 Interest. Each Note shall bear interest computed
         daily from the Second Supplemental Closing Date until final repayment
         in full of said Note in accordance with Section 2.4 of this Agreement.
         Each note shall bear interest at a rate of ten percent per annum (10%)
         to be applied to the principal amount of the Note as set forth therein
         until final repayment in full of said Note. Interest on the Loan and
         the Notes shall be due and payable on the Maturity Date and continuing
         thereafter until the Loan and Notes are repaid in full.

         8.       Annex 1 to the Loan Agreement is hereby amended by deleting
Annex 1 in its entirety and substituting therefor a new Annex 1 to read as
follows:

<TABLE>
<CAPTION>
                                                                   Proportionate       Allocation of Initial
Lender                                    Proportionate Share     Amount of Loan             Warrants
------                                    -------------------     --------------       ---------------------
<S>                                       <C>                     <C>                  <C>
Hanseatic Americas LDC
450 Park Avenue, Suite 2302
New York, New York 10022                           50%                $2,209,187              471,429

Environmental Opportunities Fund II, L.P.
c/o Sanders Morris Harris
3100 Chase Tower                                 10.7%                $  472,766              100,886
600 Travis Street, Suite 3100

Houston, Texas 77002
Environmental Opportunities Fund II
(Institutional), L.P.
c/o Sanders Morris Harris
3100 Chase Tower
600 Travis Street, Suite 3100                    39.3%                $1,736,421              370,543
Houston, Texas 77002
</TABLE>

         9.       Exhibit A to the Loan Agreement is hereby deleted in its
entirety and Exhibit A annexed hereto is hereby substituted therefor.

         10.      Except as specifically amended hereby, the Loan Agreement is
and remains unmodified and in full force and effect and is hereby ratified and
confirmed.

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<PAGE>
         11.      Contemporaneously with the execution of this Amendment,
Lenders shall deliver the Outstanding Notes to the Borrower. Contemporaneously
with the execution of this Amendment, the Borrower shall (i) cancel the
Outstanding Notes and (ii) deliver the New Notes to the Lenders, in the form
required by the Loan Agreement, as amended hereby and acceptable to the Lenders.

         12.      Contemporaneously herewith, the parties hereto shall
execute and deliver an Amendment to the Security Agreement in the form of
Exhibit B annexed hereto.

         13.      This Amendment shall be deemed a contract made under the laws
of the State of New York and for all purposes shall be governed by and construed
in accordance with the laws of such State applicable to contracts made and to be
performed entirely within such State.

         14.      This Amendment may be executed in counterparts and each of
such counterparts shall for all purposes be deemed to be an original, and such
counterparts shall constitute but one and the same instrument.

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<PAGE>
         IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
duly executed as of the date first above written.

SYSTEMONE TECHNOLOGIES INC.

By: /s/ Paul I. Mansur
    ------------------
    Name:  Paul I. Mansur
    Title: Chief Executive Officer

LENDERS

ENVIRONMENTAL OPPORTUNITIES FUND II, L.P.            HANSEATIC AMERICAS LDC
ENVIRONMENTAL OPPORTUNITIES FUND II
(INSTITUTIONAL), L.P.                                By:  Hanseatic Corporation

By: Fund II Mgt. Co., LLC                            By: /s/ Paul A. Biddelman
General Partner                                          ----------------------
                                                     Name:   Paul A. Biddelman
                                                     Title:  President

By:/s/ Bruce McMaken
   -----------------
Name:  Bruce McMaken
Title: Manager

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