PLEDGE AGREEMENT

      This Pledge  Agreement (the  "Agreement") is entered into as of the 15th
day of March,  2002 between  HydroChem  Holding,  Inc.  ("Lender")  and B. Tom
Carter, Jr.  ("Pledgor").

      WHEREAS,  Pledgor is indebted to Lender in the aggregate  amount of Four
Hundred  Thirty  Four  Thousand  Three  Hundred  Sixty One and 95/100  Dollars
($434,361.95)  for  principal  and  accrued  interest  through the date hereof
pursuant  to a certain  Secured  Promissory  Note dated as of February 9, 2001
from Pledgor to Lender (the "Old Note"); and

      WHEREAS,  under a Pledge  Agreement  dated as of  February  9, 2001 (the
"Old Pledge  Agreement")  between Pledgor and Lender, the Old Note was secured
by the pledge of Three  Hundred  Sixty  Thousand  One Hundred  Four  (360,104)
shares of the Lender's  Class A Common  Stock which  shares were  purchased at
various times pursuant to stock option exercises by Pledgor; 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
Thirty Four Thousand Three Hundred Sixty One and 95/100 Dollars  ($434,361.95)
with interest as therein  specified (the "Note") which is in substitution  and
replacement of the Old Note; 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
Agreement.

      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)  360,104   shares  of  the  Lender's   Class  A  Common  Stock
registered  in the name of Pledgor  and  represented  by the  following  stock
certificates:
<TABLE>
<CAPTION>
  Certificate Number         Date of Certificate           Number of Shares
  ------------------         -------------------           ----------------
      <S>                     <C>                           <C>
      CA-28                   April 9, 1998                 285,601

      CA-31                   April 30, 1999                 43,539

      CA-33                   May 15, 2000                   16,089

      CA-35                   February 9, 2001               14,875
</TABLE>

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<PAGE>

            (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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<PAGE>

      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.  mail,  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   supersedes   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
                                    -----------------
                                    B. Tom Carter, Jr.

                                    LENDER:

                                    HydroChem Holding, Inc.

                                    By:/s/ Kelvin Collard
                                       -------------------
                                    Kelvin Collard, Vice President and
                                    Chief Financial Officer


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