Document:

SECURED PROMISSORY NOTE

$411,402.45                      Deer Park, Texas              February 9, 2001

        FOR VALUE RECEIVED,  B. Tom Carter, Jr. ("Maker") hereby promises to pay
to the order of HydroChem Holding, Inc., a Delaware corporation  ("Payee"),  the
principal  amount of Four Hundred  Eleven  Thousand  Four Hundred Two and 45/100
Dollars  ($411,402.45)  plus  interest  thereon  at the rate of Five and  07/100
percent (5.07%)  compounded  annually,  and payable as provided herein in lawful
money of the United  States of America,  at Deer Park,  Texas,  or at such other
place as Payee of this Note may from time to time designate by written notice to
Maker.

        The principal amount of this Note and all accrued interest thereon shall
be due and payable  upon the earlier of February 8, 2007 or any  termination  of
Maker's employment with the Payee or Payee's wholly-owned subsidiary,  HydroChem
Industrial Services, Inc., but not earlier than February 8, 2004.

        Of the principal  amount of this Note,  Fourteen  Thousand Eight Hundred
Seventy  Five and 00/100  Dollars  ($14,875.00)  are in full payment for certain
shares of the Payee's Class A Common Stock being acquired by the Maker as of the
date hereof  pursuant to the  exercise of two stock  options each at an exercise
price of One Dollar ($1.00) per share. The balance of the principal represents a
substitution  and replacement of Maker's  Secured  Promissory  Notes  (including
accrued interest  thereon) dated April 30, 1999 and May 15, 2000,  respectively,
to Payee.

        Pursuant to a Pledge  Agreement of even date herewith  between Maker and
Payee, and as more specifically  described therein,  this Note is secured by the
pledge of certain  shares of common stock of Payee which are owned  beneficially
and of record by Maker,  and which  include,  but are not limited to, the shares
being  acquired  by the  Maker  pursuant  to  the  aforementioned  stock  option
exercises.

        This Note may be prepaid in whole or in part without premium or penalty.

        If this Note is placed in the hands of an attorney for collection  after
default, or if all or any part of the indebtedness represented hereby is proved,
established or collected in any court or in any bankruptcy, receivership, debtor
relief, probate or other court proceedings,  then Maker agrees to pay reasonable
attorneys'  fees and collection  costs to Payee in addition to the principal and
interest payable hereunder.

        If default is made in the payment of the  principal  or  interest  under
this Note,  or if a default  occurs  under any other  instrument  evidencing  or
securing  payment  hereof,  then in any  one or more  such  events,  the  entire
principal balance and accrued interest owing hereon shall at once become due and
payable,  at the option of Payee.  Failure to  exercise  this  option  shall not

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constitute  a waiver  of the  right  to  exercise  the same in the  event of any
subsequent default.

        Maker,  signers,  sureties,  and endorsers of this Note severally  waive
notice of  acceleration  of maturity if such shall occur,  demand,  presentment,
notice of dishonor,  diligence in  collecting,  grace,  notice and protest,  and
agree to one or more  extensions  for any period or periods of time and  partial
payments, before or after maturity, without prejudice to Payee.

        THIS NOTE SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS
OF THE STATE OF TEXAS.

                                     MAKER:

                                                   /s/ B. Tom Carter, Jr.
                                                   ----------------------
                                                   B. Tom Carter, Jr.
                                                   5956 Sherry Lane
                                                   Suite #930
                                                   Dallas, Texas  75225

                                       2PLEDGE AGREEMENT

        This Pledge  Agreement  (the  "Agreement") is entered into as of the 9th
day  of  February  2001  between  HydroChem Holding, Inc. ("Lender") and  B. Tom
Carter, Jr.  ("Pledgor").

        WHEREAS,  Pledgor is indebted to Lender in the aggregate amount of Three
Hundred  Ninety Six  Thousand  Five  Hundred  Twenty  Seven and  45/100  Dollars
($396,527.45)  for  principal  and  accrued  interest  through  the date  hereof
pursuant to two certain Secured  Promissory Notes dated as of April 30, 1999 and
May 15, 2000, respectively, from Pledgor to Lender (the "Old Notes"); and

        WHEREAS,  under two Pledge Agreements dated as of April 30, 1999 and May
15, 2000,  (the "Old Pledge  Agreements")  between  Pledgor and Lender,  the Old
Notes are secured by the pledge of Three Hundred Forty Five Thousand Two Hundred
Twenty Nine (345,229) shares of the Lender's Class A Common Stock (the "Existing
Shares")  represented by stock certificates CA-28, CA-31 and CA-33, which shares
were purchased pursuant to earlier stock option exercises by Pledgor; and

        WHEREAS, as of the date hereof, Pledgor has exercised certain additional
stock  options to purchase,  for One Dollar  ($1.00) per share,  an aggregate of
Fourteen Thousand Eight Hundred Seventy Five (14,875) shares of Lender's Class A
Common Stock (the "Additional  Shares")  represented by Stock Certificate CA-35;
and

        WHEREAS, Pledgor has executed and delivered a Secured Promissory Note to
Lender  dated as of the date  hereof in the  principal  amount  of Four  Hundred
Eleven Thousand Four Hundred Two and 45/100 Dollars  ($411,402.45) with interest
as therein  specified  (the "Note") which is in full payment for the  Additional
Shares and in substitution and replacement of the Old Notes; and

        WHEREAS,  Pledgor desires to pledge all of the Stock Collateral (as such
term  is   hereinafter   defined)  as  collateral  and  security  for  Pledgor's
obligations and duties under the Note and this Agreement, and to enter into this
Pledge Agreement in replacement and substitution of the Old Pledge Agreements.

        NOW,  THEREFORE,  for  and in  consideration  of the  premises  and  the
covenants herein  contained,  and in consideration of the extension of credit to
Pledgor as evidenced by the Note, the parties hereto agree as follows:

        1.  Pledge of Stock Collateral.  As  collateral  and  security  for  the
prompt and full  performance of all duties and  obligations of Pledgor under the
Note and this  Agreement,  Pledgor  hereby  pledges,  assigns and transfers unto
Lender,  and  grants a  security  interest  to  Lender  in and to the  following
property of Pledgor (collectively, the "Stock Collateral"):

               (a)  The Existing Shares and the Additional Shares (collectively,
the "Shares")

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               (b)  All stock rights, rights to subscribe, dividends (including,
but not limited to, cash dividends, stock dividends, dividends paid in stock and
liquidating  dividends),  and any other rights and property interest (including,
but  not  limited  to,  accounts,   contract  rights,  instruments  and  general
intangibles) arising out of or relating to the Shares;

               (c)  All other or additional (or less) stock or other  securities
or property (including cash) paid or distributed in respect of the Shares by way
of stock split,  spin off,  reclassification,  combination  of shares or similar
corporate rearrangement;

               (d)  All other or additional (or less) stock or other  securities
or property  (including  cash) paid or  distributed  in respect of the Shares by
reason of any consolidation,  merger,  exchange of stock,  conveyance of assets,
liquidation or similar corporate reorganization; and

               (e)  All  proceeds (both  cash and  non-cash)  of the  foregoing,
whether now or hereafter arising under the foregoing.

The  above  referenced  certificates  representing  the  Shares,  together  with
irrevocable stock powers executed in blank, are herewith  delivered to Lender to
hold pursuant to the terms of this Agreement.

        2.  Dividends.  So long  as  there  exists  no  default by Pledgor under
the Note or  this  Agreement during  the  term  hereof,  all dividends and other
amounts with respect to the Stock  Collateral shall be paid to
the Pledgor.

        3.  Voting  Rights.  During the term of this  Agreement,  and so long as
Pledgor is not in default in the  performance of any of the terms of the Note or
this  Agreement,  Pledgor  shall have the sole and  exclusive  right to vote the
Stock  Collateral on all corporate  questions before the stockholders of Lender,
and Lender  shall  execute  and  deliver  to Pledgor in a due and timely  manner
proxies in favor of Pledgor to this end.

        4.  Representations  and Warranties.  Pledgor represents and warrants to
Lender (i) that the Shares are  validly  issued,  fully paid and  nonassessable,
(ii) that the Shares are validly  pledged to Lender in accordance  with law, and
(iii) that Pledgor has, and will have, good and marketable  title to the Shares,
free and clear of all liens and encumbrances  (other than the security  interest
granted herein).

        5.  Covenants.  Until   full   performance  of  Pledgor's   duties   and
obligations  under the Note and this  Agreement,  Pledgor  shall (i)  deliver to
Lender (a) immediately  upon Pledgor's  receipt of any stock or other securities
paid or distributed in respect of the Shares, the certificates representing such
stock or securities,  and (b) irrevocable stock powers executed in blank for all
such stock or securities;  (ii) defend, at Pledgor's sole expense,  the title to
the Stock  Collateral or any part thereof;  and (iii) promptly,  upon request by
Lender, execute,  acknowledge and deliver any financing statement,  endorsement,
renewal,   affidavit,   deed,  assignment,   continuation  statement,   security
agreement,  certificate  or other  document  as Lender  may  require in order to
perfect,  preserve,  maintain,  protect,  continue  and/or  extend  the lien and
security interest of Lender under this Agreement and the priority thereof.

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        6.  Full  Performance.  Upon full performance  of  Pledgor's  duties and
obligations  under the Note and this Agreement,  Lender shall deliver to Pledgor
all of the Stock  Collateral that remains  pledged  hereunder and this Agreement
shall thereupon terminate.

        7.  Default.  Pledgor  shall  be in  default under this Agreement on the
occurrence of any of the following events or conditions:

               (a)  Failure to  make any payment in accordance with the terms of
the Note; or

               (b)  Pledgor's failure to observe,  keep or perform any covenant,
agreement  or  condition  required by this  Agreement  to be  observed,  kept or
performed; or

               (c)  Pledgor's insolvency, or the appointment  of an assignee for
the benefit of creditors  or of a receiver  for Pledgor,  or in the event that a
petition under any provision of the Federal Bankruptcy Act is filed either by or
against Pledgor.

        8.  Remedies.  Upon the occurrence of any event of default,  in addition
to any other right or remedy that Lender may then have under the Texas  Business
and Commerce Code or otherwise, Lender may sell, assign and deliver, in its sole
discretion,  all or any part of the Stock Collateral in one or more parcels, and
all right,  title and interest,  claim and demand therein,  at public or private
sale, for cash or other property,  upon credit or for future  delivery,  Pledgor
hereby waiving and releasing any and all equity or right of redemption.

        9.  No Waiver of Rights or  Remedies.  No failure  or delay by Lender in
exercising any right,  power or privilege under the Note or this Agreement shall
operate as a waiver  thereof,  and no single or partial  exercise  thereof shall
preclude any other or future exercise of any other right, power or privilege.

        10. Notice.  Any notice required or permitted  hereunder  shall be given
in  writing  and  shall be deemed  effective  when  delivered  in person or when
deposited in the U.S.  mails,  postage  prepaid,  for delivery as  registered or
certified mail, return receipt requested, and addressed as follows:

                             If to Pledgor:  B. Tom Carter, Jr.
                                             5956 Sherry Lane
                                             Suite #930
                                             Dallas, Texas  75225

                             If to Lender:
                                             HydroChem Industrial Services, Inc.
                                             900 Georgia Avenue
                                             Deer Park, Texas 77536
                                             Attention: General Counsel

(or to such other address as may be stated in written  notices  furnished by any
party to the other party).

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<PAGE>

        11. Governing Law.  This  Agreement shall be governed  by  and construed
under and in  accordance  with the Texas  Business and  Commerce  Code and other
applicable laws of the State of Texas.

        12. Parties  Bound.  This Agreement shall be binding on and inure to the
benefit  of  the  parties  hereto  and  their   respective   heirs,   executors,
administrators, representatives, successors and assigns.

        13. Severability. In case any one or more of the provisions contained in
this  Agreement  shall,  for any  reason,  be held to be  invalid,  illegal,  or
unenforceable in any respect,  such invalidity,  illegality or  unenforceability
shall not  affect  any  other  provision  hereof,  and this  Agreement  shall be
construed as if such invalid,  illegal or unenforceable provision had never been
contained herein.

        14. Entire   Agreement.    This   Agreement   constitutes   the   entire
understanding between the parties with respect to the subject matter hereof, and
it supercedes  all other prior or  contemporaneous  agreements,  understandings,
restrictions  warranties or representations  between the parties including,  but
not  limited  to, the Old Pledge  Agreements  which are hereby  cancelled.  This
Agreement  may be amended or waived in the future  only by a written  instrument
signed by both parties.

        15. Headings. The headings contained in this Agreement are for reference
purposes  only and shall not affect in any way the meaning of this  Agreement or
its interpretation.

        16. Stockholders Agreement.  Notwithstanding any other provision of this
Agreement, Lender hereby acknowledges that is takes the Stock Collateral subject
to the terms and conditions of that certain  Stockholders  Agreement dated as of
December  15,  1993,  as amended,  by and among  Lender and  certain  holders of
Lender's capital stock.

            IN WITNESS WHEREOF,  the  parties  have  executed this Agreement and
caused the same to be duly delivered on the day and year  hereinabove  first set
forth.

                                          PLEDGOR:

                                          /s/ B. Tom Carter, Jr.
                                          ----------------------
                                          B. Tom Carter, Jr.

                                          LENDER:

                                          HydroChem Holding, Inc.

                                          By: /s/ Pelham H. A. Smith
                                              ----------------------
                                              Pelham H.A. Smith, Vice President

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