PLEDGE AGREEMENT

         This Pledge Agreement (the  "Agreement") is entered into as of the 30th
day of April, 1999 between HydroChem Holding, Inc. ("Lender") and B. Tom Carter,
Jr. ("Pledgor").

         WHEREAS,  Pledgor is indebted to Lender in the amount of Three  Hundred
Two  Thousand  Eight  Hundred  Sixteen  and  86/100  Dollars  ($302,816.86)  for
principal and accrued  interest through the date hereof pursuant to that certain
Secured  Promissory  Note dated  April 9, 1998 from  Pledgor  to Lender,  as the
assignee of HydroChem Industrial Services, Inc. (the "Old Note"); and

         WHEREAS,  under a Pledge  Agreement dated as of April 9, 1998 (the "Old
Pledge Agreement") between Pledgor and Lender as the assignee of HydroChem,  the
Old Note is  secured by the  pledge of Two  Hundred  Eighty  Five  Thousand  Six
Hundred One (285,601) shares of the Lender's Class A Common Stock (the "Existing
Shares")  represented by stock certificate CA-28, which shares were purchased on
said date  pursuant  to the partial  exercise  by Pledgor of two  certain  stock
options; and

         WHEREAS, as of the date hereof,  Pledgor has further exercised the said
two stock options to purchase,  for One Dollar ($1.00) per share,  an additional
Forty Three Thousand Five Hundred Thirty Nine (43,539)  shares of Lender's Class
A Common Stock (the "Additional Shares") represented by Stock Certificate CA-31;
and

         WHEREAS,  Pledgor has executed and delivered a Secured  Promissory Note
to Lender dated as of the date hereof in the  principal  amount of Three Hundred
Forty Six Thousand  Three  Hundred Fifty Five and 86/100  Dollars  ($346,355.86)
with  interest as therein  specified  (the "Note") which is full payment for the
Additional Shares and 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)  The   Existing   Shares   and   the   Additional   Shares
(collectively, the "Shares")

                  (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




<PAGE>



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.

         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


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<PAGE>



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  Agreement  which is 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 all 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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