EXHIBIT B

                                PLEDGE AGREEMENT

        This Pledge Agreement (the  "Agreement") is entered  into as of the 15th
day of May,  2000  between HydroChem Holding, Inc. ("Lender") and B. Tom Carter,
Jr.  ("Pledgor").

        WHEREAS, Lender has granted a stock option (the "Stock Option") dated as
of the date  hereof to Pledgor  under  which an  aggregate  of 16,089  shares of
Lender's  Class  Common Stock (the  "Shares")  may be purchased by Pledgor at an
exercise price of $1.00 per share; and

        WHEREAS,  simultaneously  herewith,  Pledgor is (i) exercising the Stock
Option to  purchase  the Shares  which will be  represented  by  Lender's  stock
certificate no. CA-33, and (ii) executing a Secured Promissory Note (the "Note")
to  Lender  dated as of the date  hereof  in the  principal  amount  of  Sixteen
Thousand  Eighty  Nine 00/100  Dollars ($  16,089.00)  with  interest as therein
specified which is in full payment for the Shares; 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.

        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  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 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.

<PAGE>


The above  referenced  certificate  representing  the Shares,  together  with an
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  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.

                                       2
<PAGE>

        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 No. 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).

        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

                                       3
<PAGE>

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

                                       4