[EXECUTION COPY]

                                 AMENDMENT NO. 4

         AMENDMENT  NO. 4 dated as of January  [__],  2000 to the Note  Purchase
Agreement referred to below, between:

         NUCO2 INC., a corporation duly organized and validly existing under the
laws of the State of Florida (the "Company");

         each of the  Subsidiaries  of the Company  appearing  under the caption
"SUBSIDIARY  GUARANTORS"  on the  signature  pages  hereto  (each a  "Subsidiary
Guarantor" and, collectively,  the "Subsidiary  Guarantors";  and, together with
the Company, the "Obligors"); and

         each of the Investors  appearing  under the caption  "INVESTORS" on the
signature pages hereto (each, an "Investor", and collectively, the "Investors").

         WHEREAS,  the  Obligors  and  the  Investors  are  party  to  a  Senior
Subordinated Note Purchase Agreement dated as of October 31, 1997 (as heretofore
modified and supplemented  and in effect on the date hereof,  the "Note Purchase
Agreement"), pursuant to which the Company issued (or will issue) its 12% Senior
Subordinated Notes in an aggregate  principal amount of up to $45,000,000 to the
Investors; and

         WHEREAS,  the parties to the Note Purchase  Agreement wish to amend the
Note Purchase Agreement to make certain modifications thereto;

         Accordingly, the parties hereto hereby agree as follows:

         Section 1.  Definitions.  Except as otherwise defined in this Amendment
No. 4, terms defined in the Note  Purchase  Agreement are used herein as defined
therein.

         Section  2.  Amendments  to Note  Purchase  Agreement.  Subject  to the
satisfaction  of the  conditions  precedent  specified  in Section 4 below,  but
effective as of the date hereof, the Note Purchase Agreement shall be amended as
follows:

         A. References in the Note Purchase  Agreement to "this  Agreement" (and
indirect references such as "hereunder",  "hereby", "herein" and "hereof") shall
be deemed to be references to the Note Purchase Agreement as amended hereby.

         B. Section 8.09 of the Note Purchase  Agreement shall be amended in its
entirety to read as follows:

         ................"SECTION 8.09   Financial Covenants.


         (a) Interest  Coverage Ratio.  The Company will not permit the Interest
Coverage  Ratio to be less than the following  respective  ratios as at the last
day of each fiscal quarter during the following respective periods:

                    Period                                 Ratio

               From April 1, 1999
                through March 31, 2000                  1.25 to 1.00

               From April 1, 2000
                through June 30, 2000                   1.50 to 1.00

               From July 1, 2000
                through September 30, 2000              1.65 to 1.00

               From October 1, 2000
                through December 31, 2000               1.75 to 1.00

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               From January 1, 2001
                through March 31, 2001                  2.00 to 1.00

               From April 1, 2001
                through June 30, 2001                   2.25 to 1.00

               From July 1, 2001
                through September 30, 2001              2.40 to 1.00

               From October 1, 2001
                and at all times thereafter             2.50 to 1.00

         (b) Total Net Funded Debt Coverage  Ratio.  The Company will not permit
the Total Net Funded  Debt  Coverage  Ratio to exceed the  following  respective
ratios at any time during the following respective periods:

                        Period                         Ratio

               From October 1, 1999
                through December 31, 1999           5.50 to 1.00

               From January 1, 2000
                through March 31, 2000              5.00 to 1.00

               From April 1, 2000
                and at all times thereafter         4.50 to 1.00

                  (c) Minimum Net Worth. The Company shall at all times maintain
Consolidated  Net Worth of not less than the sum of (a)  $37,5000,000,  (b) plus
50% of the cumulative  Consolidated Net Income for each fiscal quarter ending on
or after December 31, 1997 (but  specifically not including any Consolidated Net
Loss for any such fiscal  quarter) plus (c) the  cumulative  net proceeds of all
equity  offerings (if any) made by the Company for each fiscal quarter ending on
or after September 30, 1997."

         Section 3.  Representations and Warranties.  The Company represents and
warrants to the Investors that: (i) the representations and warranties set forth
in Article VI of the Note Purchase  Agreement  (as amended  hereby) are true and
complete  on the date  hereof as if made on and as of the date  hereof and as if
each  reference  in said  Article  VI to "this  Agreement"  (or words of similar
import) referred to the Note Purchase Agreement as amended by this Amendment No.
4 (except that (x) certain of the  indebtedness  listed in Schedule  6.12 to the
Note  Purchase  Agreement  has been paid off by the  Company,  (y) the number of
validly  issued and  outstanding  shares of common  stock,  par value $0.001 per
share,  referred to in Section 6.13 of the Note Purchase  Agreement is 7,216,997
and (z) the number of  outstanding  options  granted under the  Company's  stock
option plans has changed); and (ii) no Default has occurred and is continuing.

         Section 4. Conditions  Precedent.  As provided in Section 2 above,  the
amendments  to the Note  Purchase  Agreement  set forth in said  Section 2 shall
become effective,  as of the date hereof, upon the satisfaction of the following
conditions:

                  (a) Amendment No. 4. The execution and delivery of one or more
counterparts of this Amendment No. 4 by the Obligors and the Required Investors,
and receipt by the  Investors of evidence  that the lenders  party to the Senior
Credit Agreement shall have approved this Amendment No. 4.

                  (b) Second  Amendment to Senior Credit  Agreement.  Receipt by
the Investors of a copy of the Second  Amendment to the Senior Credit  Agreement
as executed by the parties thereto.

                  (c) Other  Documents.  Receipt by the  Investors of such other
documents  as any  Investor or special  New York  counsel to the  Investors  may
reasonably request.

         Section 5. Miscellaneous.  Except as herein provided, the Note Purchase
Agreement  shall remain  unchanged and in full force and effect.  This Amendment
No. 4 may be executed in any number of counterparts, all of which taken together

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shall  constitute one and the same amendatory  instrument and any of the parties
hereto may execute this  Amendment No. 4 by signing any such  counterpart.  This
Amendment No. 4 shall be governed by, and construed in accordance  with, the law
of the State of New York.


         IN WITNESS WHEREOF, the parties hereto have caused this Amendment No. 4
to be duly executed and delivered as of the day and year first above written.

                                           NUCO2 INC.


                                           By: /s/ Joann Sabatino
                                               ---------------------------------
                                               Title:  Chief Financial Officer
                                                       and Treasurer


                                           SUBSIDIARY GUARANTORS

                                           NUCO2 ACQUISITION CORP.


                                           By: /s/ Eric M. Wechsler
                                               ---------------------------------
                                               Title: Vice President


                                           KOCH COMPRESSED GASES, INC.



                                           By: /s/ Eric M. Wechsler
                                               ---------------------------------
                                               Title: Vice President




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                                           INVESTORS


                                           CHASE EQUITY ASSOCIATES, LLC
                                           (f/k/a Chase Equity Associates L.P.)

                                           By Chase Capital Partners,
                                            its Manager


                                           By: /s/ Richard D. Waters
                                               -------------------------
                                               Title: General Partner


                                           DK ACQUISITION PARTNERS, L.P.

                                           By M.H. Davidson & Co.,
                                            its general partner


                                           By_________________________
                                             Title:


                                           EMPIRE  INSURANCE  COMPANY,
                                           as executed on their behalf
                                           by their Investment Manager,
                                           Cohanzick Management, L.L.C.


                                           By_________________________
                                             Title:


                                           ORIX USA CORPORATION


                                           By_________________________
                                             Title:




<PAGE>


                               PAINEWEBBER HIGH INCOME FUND,
                               a series of PaineWebber Managed Investments Trust


                               By_________________________
                                 Title:


                               SUNTRUST BANKS, INC.


                               By: /s/ Robert Dudiak
                                   ---------------------
                                   Title: Group Vice President