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                                  EXHIBIT 10.2
                                 PROMISSORY NOTE

$930,000.00                                                    November 30, 2001

        FOR VALUE RECEIVED, Clayton Lau, an individual residing in Harris
County, Texas and Houston Dynamic Service, Inc., a Texas corporation, jointly
and severally ("Maker"), promise to pay to the order of Mountain Compressed Air,
Inc, a Texas corporation ("Payee"), in lawful money of the United States of
America, the principal sum of Nine Hundred Thirty Thousand Dollars
($930,000.00), together with interest in arrears on the unpaid principal balance
at an annual rate equal to 7%, in the manner provided below. Interest shall be
calculated on the basis of a year of 365 or 366 days, as applicable, and charged
for the actual number of days elapsed.

        This Note has been executed and delivered pursuant to and in accordance
with the terms and conditions of the Stock Purchase Agreement, effective as of
November 30, 2001, by and between Clayton Lau and Payee (the "Agreement"), and
is subject to the terms and conditions of the Agreement, which are, by this
reference, incorporated herein and made a part hereof. Capitalized terms used in
this Note without definition shall have the respective meanings set forth in the
Agreement.

        1. PAYMENTS

               1.1 PRINCIPAL AND INTEREST

        The principal amount of this Note shall be due and payable in one
installment on November 30, 2007. Interest on the unpaid principal balance of
this Note shall be due and payable monthly beginning on December 30, 2001 and
the same day of each succeeding month until paid in full.

               1.2 MANNER OF PAYMENT

        All payments of principal and interest on this Note shall be made by
bank check at 2466 Commerce Blvd., Grand Junction, Colorado 81505, or at such
other place in the United States of America as Payee shall designate to Maker in
writing or by wire transfer of immediately available funds to an account
designated by Payee in writing. If any payment of principal or interest on this
Note is due on a day which is not a Business Day, such payment shall be due on
the next succeeding Business Day, and such extension of time shall be taken into
account in calculating the amount of interest payable under this Note. "Business
Day" means any day other than a Saturday, Sunday or legal holiday in the State
of Texas.


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               1.3 PREPAYMENT

        Maker may, without premium or penalty, at any time and from time to
time, prepay all or any portion of the outstanding principal balance due under
this Note, provided that each such prepayment is accompanied by accrued interest
on the amount of principal prepaid calculated to the date of such prepayment.
Any partial prepayments shall be applied to installments of principal in inverse
order of their maturity. In the event that Maker prepays the principal of the
Note in an aggregate amount in excess of $400,000.00, the Payee agrees to reduce
the remaining principal by fifteen percent (15%).



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        2. DEFAULTS

               2.1 EVENTS OF DEFAULT

        The occurrence of any one or more of the following events with respect
to Maker shall constitute an event of default hereunder ("Event of Default"):

               (a) If Maker shall fail to pay when due any payment of principal
or interest on this Note and such failure continues for ten (10) days after
Payee notifies Maker therein writing.

               (b) If, pursuant to or within the meaning of the United States
Bankruptcy Code or any other federal or state law relating to insolvency or
relief of debtors (a "Bankruptcy Law"), Maker shall (i) commence a voluntary
case or proceeding; (ii) consent to the entry of an order for relief against it
in an involuntary case; (iii) consent to the appointment of a trustee, receiver,
assignee, liquidator or similar official; (iv) make an assignment for the
benefit of its creditors; or (v) admit in writing its inability to pay its debts
as they become due.

               (c) If a court of competent jurisdiction enters an order or
decree under any Bankruptcy Law that (i) is for relief against Maker in an
involuntary case, (ii) appoints a trustee, receiver, assignee, liquidator or
similar official for Maker or substantially all of Maker's properties, or (iii)
orders the liquidation of Maker, and in each case the order or decree is not
dismissed within 120 days.

               (d) Make any additional investment in fixed assets in any one
fiscal year in excess of an aggregate of $50,000.00 without prior written
approval of Payee.

               (e) Create, incur, assume or permit to exist any indebtedness or
liabilities resulting from borrowings, loans or advances, whether secured or
unsecured, matured or unmatured, liquidated or unliquidated, joint or several,
except the liability of Maker to Payee in excess of $50,000.00, without prior
written approval of Payee.

               (f) Merge into or consolidate with any other entity; make any
substantial change in the nature of Maker's business as conducted as of the date
hereof; acquire all or substantially all of the assets of any other entity; nor
sell, lease, transfer, or otherwise dispose of all or a substantial or material
portion of Maker's assets except in the ordinary course of its business.

               (g) Guaranty or become liable in any way as surety, endorser,
accommodation endorser or otherwise for, nor pledge or hypothecate any assets of
Maker as security for, any liabilities or obligations of any other person or
entity, except any of the foregoing in favor of Payee.


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               (h) Declare or pay any dividend or distribution either in cash,
stock or any other property on Maker's stock now or hereafter outstanding, nor
redeem, retire, repurchase or otherwise acquire any shares of any class of
Maker's stock now or hereafter outstanding.

               (i) Mortgage, pledge, grant or permit to exist a security
interest in, or lien upon, all or any portion of Maker's assets now owned or
hereafter acquired, except any of the foregoing in favor of Payee unless such
interest is created as a secondary lien to Payee's security interest.

               (j) Increase or pay compensation to officers or stockholders of
the Company in an amount greater than paid the previous year, except in the case
of Clayton Lau total compensation including salary and bonus (but excluding
principal and interest on this Note) paid for any year may not exceed
$175,000.00 until this Note is paid in full.

                      2.2 NOTICE BY MAKER

        Maker shall notify Payee in writing within five days after the
occurrence of any Event of Default of which Maker acquires knowledge.

                      2.3 REMEDIES

        Upon the occurrence of an Event of Default hereunder (unless all Events
of Default have been cured or waived by Payee), Payee may, at its option, (i) by
written notice to Maker, declare the entire unpaid principal balance of this
Note, together with all accrued interest thereon, immediately due and payable
regardless of any prior forbearance, (ii) exercise any and all rights and
remedies available to it under applicable law, including, without limitation,
the right to collect from Maker all sums due under this Note and (iii) notify
Maker of default and elect to obtain a sixty percent (60%) equity interest on a
fully diluted basis in Maker. Payee's election to obtain a sixty percent (60%)
interest in Maker shall satisfy in full the Maker's obligations under the Note
and Security Agreement. Maker shall pay all reasonable costs and expenses
incurred by or on behalf of Payee in connection with Payee's exercise of any or
all of its rights and remedies under this Note, including, without limitation,
reasonable attorneys' fees.

                      3. MISCELLANEOUS

                      3.1 WAIVER

        The rights and remedies of Payee under this Note shall be cumulative and
not alternative. No waiver by Payee of any right or remedy under this Note shall
be effective unless in a writing signed by Payee. Neither the failure nor any
delay in exercising any right, power or privilege under this Note will operate
as a waiver of such right, power or privilege and no single or partial exercise
of any such right, power or privilege by Payee will preclude any other or
further exercise of such right, power or privilege or the exercise of any other
right, power or privilege. To the maximum extent permitted by


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applicable law, (a) no claim or right of Payee arising out of this Note can be
discharged by Payee, in whole or in part, by a waiver or renunciation of the
claim or right unless in a writing, signed by Payee; (b) no waiver that may be
given by Payee will be applicable except in the specific instance for which it
is given; and (c) no notice to or demand on Maker will be deemed to be a waiver
of any obligation of Maker or of the right of Payee to take further action
without notice or demand as provided in this Note. Maker hereby waives
presentment, demand, protest and notice of dishonor and protest.

                      3.2 NOTICES

        Any notice required or permitted to be given hereunder shall be given in
accordance with Section 11.4 of the Agreement.

                      3.3 SEVERABILITY

        If any provision in this Note is held invalid or unenforceable by any
court of competent jurisdiction, the other provisions of this Note will remain
in full force and effect. Any provision of this Note held invalid or
unenforceable only in part or degree will remain in full force and effect to the
extent not held invalid or unenforceable.

                      3.4 GOVERNING LAW

        This Note will be governed by the laws of the State of Texas without
regard to conflicts of laws principles.

                      3.5 PARTIES IN INTEREST

        This Note shall bind Maker and its successors and assigns.

                      3.6 SECTION HEADINGS, CONSTRUCTION

        The headings of Sections in this Note are provided for convenience only
and will not affect its construction or interpretation. All references to
"Section" or "Sections" refer to the corresponding Section or Sections of this
Note unless otherwise specified.

                      3.7 SECURITY AGREEMENT

        This Note is secured by that certain Security Agreement between Maker
and Payee of even date herewith.

        All words used in this Note will be construed to be of such gender or
number as the circumstances require. Unless otherwise expressly provided, the
words "hereof" and "hereunder" and similar references refer to this Note in its
entirety and not to any specific section or subsection hereof.


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        IN WITNESS WHEREOF, Maker has executed and delivered this Note as of the
date first stated above.


                                         MAKER:

                                         ____________________________________
                                         Clayton Lau

                                         HOUSTON DYNAMIC SERVICE, INC.


                                         By:_________________________________
                                            Clayton Lau, President