Document:

Exhibit 10.10

                     THIRD AMENDMENT TO AMENDED AND RESTATED
                           REVOLVING CREDIT AGREEMENT

            THIS  THIRD  AMENDMENT  TO AMENDED  AND  RESTATED  REVOLVING  CREDIT
AGREEMENT (this  "Amendment") made as of May 12, 2000 by and among NUCO2 INC., a
Florida   corporation  (the   "Company"),   SUNTRUST  BANK,  a  Georgia  banking
corporation (formerly named SunTrust Bank, South Florida,  National Association,
a  national  banking  association)  ("SunTrust"),   BANK  AUSTRIA  CREDITANSTALT
CORPORATE FINANCE, INC., a Delaware corporation (the "Documentation Agent"), THE
PROVIDENT BANK, an Ohio banking  corporation,  BANK LEUMI LE-ISRAEL B.M.,  Miami
Agency,  IBJ WHITEHALL  BUSINESS  CREDIT  CORPORATION,  a New York  corporation,
HAMILTON  BANK,  N.A., a national  banking  association,  and any other banks or
other  lending  institutions  that  are or will  become  parties  to the  Credit
Agreement (as defined below) (collectively, the "Lenders" and each individually,
a "Lender"),  and SUNTRUST BANK, a Georgia banking  corporation  (formerly named
SunTrust  Bank,  South  Florida,   National  Association,   a  national  banking
association), as agent for the Lenders.

                             PRELIMINARY STATEMENTS:

            The  Company,  Agent and the  Lenders  are  parties to that  certain
Amended  and  Restated  Revolving  Credit  Agreement  dated as of May 4, 1999 as
amended by that certain First Amendment to Amended and Restated Revolving Credit
Agreement  dated  as of June 16,  1999 and as  amended  by that  certain  Second
Amendment and Waiver to Amended and Restated Revolving Credit Agreement dated as
of February 7, 2000 (the "Credit  Agreement";  capitalized terms used herein and
not  defined  herein  shall  have the  meanings  assigned  to them in the Credit
Agreement),  pursuant to which the  Lenders  made and  continue to make  certain
financial accommodations to the Company;

            The Company has  requested,  and the Lenders have  agreed,  to amend
certain  financial  covenants and to make certain other  amendments on the terms
and subject to the conditions set forth herein.

            NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged,  the parties hereto,  intending to
be legally bound, agree as follows:

1.          Amendments to Credit Agreement.

            a.  Section 1.01 of the Credit  Agreement is hereby  amended by: (i)
replacing the  definitions of  "Applicable  Margin",  "Consolidated  Net Worth",
"EBITDA  Multiple" and "Senior Funded Debt" in their entirety with the following
definitions:

<PAGE>

            "Applicable Margin" shall mean the percentage designated below based
on the ratio of the Company's  Total Funded Debt to  Annualized  EBITDA for each
fiscal quarter-end, as indicated below:

                 Total Funded Debt to    Applicable Margin   Applicable Margin
                 Annualized EBITDA       (LIBOR Advance)    (Base Rate Advance)

Level I             < 4.00:1.00              2.75%              1.25%

Level II           => 4.00:1.00 and          3.25%              1.75%
                      < 4.75:1.00

Level III            => 4.75:1.00            3.75%              2.25%

            From the Effective Date through and including December 31, 2000, the
            Applicable  Margin on LIBOR Advances and Base Rate Advances shall be
            3.75% and 2.25% respectively.

                        "Consolidated  Net Worth" shall mean,  as of the date of
            determination,   the  sum  of,   without   duplication,   (a)  total
            shareholders'  equity  of the  Company  and  its  Subsidiaries  on a
            consolidated basis determined in accordance with GAAP and (b) the 8%
            Convertible Preferred Stock.

                        "EBITDA Multiple" shall mean (a) 3.35 from March 1, 2000
            through  and  including  June 30,  2000;  (b) 3.30 from July 1, 2000
            through and  including  July 31, 2000;  (c) 3.25 from August 1, 2000
            through and including  September 30, 2000;  (d) 3.20 from October 1,
            2000 through and including  October 31, 2000; (e) 3.10 from November
            1, 2000  through and  including  November  30,  2000;  (f) 3.05 from
            December 1, 2000 through and including  December 31, 2000;  (g) 3.00
            from January 1, 2001  through and  including  January 31, 2001;  (h)
            2.95 from February 1, 2001 through and including  February 28, 2001;
            (i) 2.90 from March 1, 2001  through and  including  March 31, 2001;
            (j) 2.85 from April 1, 2001  through and  including  April 30, 2001;
            (k) 2.80 from May 1, 2001 through and  including  May 31, 2001;  (l)
            2.75 from June 1, 2001 through and including June 30, 2001; (m) 2.70
            from July 1, 2001 through and including July 31, 2001; (n) 2.65 from
            August 1, 2001 through and including  August 31, 2001; (o) 2.60 from
            September 1, 2001 through and including  September 30, 2001; and (p)
            2.50 thereafter.

                        "Senior  Funded  Debt" shall mean all  indebtedness  for
            money  borrowed,  purchase  money  mortgages,   capitalized  leases,
            outstandings under asset securitization vehicles,  conditional sales
            contracts and similar title  retention debt  instruments,  including
            any  current  maturities  of such  indebtedness,  which by its terms
            matures more than one year from the date of any calculation  thereof
            and/or which is renewable or extendable at the option of the obligor
            to  a  date  beyond  one  year  from  such  date;   provided,   that
            Subordinated Debt shall not be included.

(ii) inserting a new sentence at the end of the definition of  "Indebtedness" to
read as follows:  "Notwithstanding the foregoing, Indebtedness shall exclude the
8% Convertible Preferred Stock."

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<PAGE>

(iii)  deleting the  definitions  of  "Applicable  Commitment  Fee  Percentage",
"Interest  Coverage Ratio",  "Maintenance  Capital  Expenditures",  "Net Worth",
"Senior Debt Leverage Ratio" and "Total Capitalization" in their entirety; and

(iv) adding the following definitions in their proper alphabetical order:

                        "8%   Convertible   Preferred   Stock"  shall  mean  the
            Company's 8% Cumulative  Convertible  Preferred Stock, no par value,
            having an aggregate initial liquidation preference of $5,000,000.

                        "Fifth Amendment to Senior Subordinated Debt" shall mean
            that certain  Amendment No. 5 to Senior  Subordinated  Note Purchase
            Agreement,  dated as of the date  hereof,  among  the  Company,  the
            Guarantors and the Investors listed therein.

                        "Total  Funded  Debt"  shall mean all  indebtedness  for
            money  borrowed,  purchase  money  mortgages,   capitalized  leases,
            outstandings under asset securitization vehicles,  conditional sales
            contracts and similar title  retention debt  instruments,  including
            any  current  maturities  of such  indebtedness,  which by its terms
            matures more than one year from the date of any calculation  thereof
            and/or which is renewable or extendable at the option of the obligor
            to a date  beyond  one year  from  such  date,  minus  cash and cash
            equivalents.

                        "Total Funded Debt Coverage  Ratio" shall mean,  for any
            fiscal period of the Company,  the ratio of (a) Total Funded Debt as
            of the last day of such fiscal period to (b) Annualized EBITDA.

            b.  Section  2.16 of the  Credit  Agreement  is  hereby  amended  by
replacing clause (c) of such Section 2.16 in its entirety with the following:

                        (c) The Company shall pay to the Agent,  for the account
            of and  distribution of the respective Pro Rata Share to each Lender
            (subject  to the  last  sentence  hereof),  a  commitment  fee  (the
            "Commitment  Fee") for the period commencing on April 1, 2000 to and
            including the Commitment  Termination  Date computed at a rate equal
            to .50%  multiplied  by the  average  daily  unused  portion  of the
            Commitments  of the  Lenders,  such fee being  payable  quarterly in
            arrears on the last day of each calendar quarter, commencing on June
            30, 2000, and on the Commitment Termination Date. The Commitment Fee
            will be  calculated  on the basis of a 360-day  year for the  actual
            number of days elapsed.

            c. Section 5.02(a) of the Credit  Agreement is hereby amended (i) to
delete  the word  "and" at the end of clause  (vi)  thereof,  (ii) to delete the
punctuation  "." at the end of clause (vii) thereof and to  substitute  therefor
the new  language  ";  and" and (iii) to add the  following  new  clause  (viii)
thereto:

                        (viii) as soon as  available  and in any event within 30
            days after the end of each month, a completed report with respect to
            accounts of the Company showing

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<PAGE>

            aging and such other matters related to accounts  receivable in such
            form as reasonably requested by the Agent.

            d.  Section  5.05 of the  Credit  Agreement  is  hereby  amended  by
replacing such Section 5.05 in its entirety with the following:

                        "Section  5.05  Maintenance  of  Books;   Inspection  of
            Property and Records; Audits.

                        (a) The  Company  shall,  and  shall  cause  each of its
            Subsidiaries to, keep proper books of record and account  containing
            complete  and accurate  entries in all  material  respects of all of
            their respective financial and business  transactions and prepare or
            cause to be prepared its annual statements and reports in accordance
            with  GAAP.  The  Company  shall,   and  shall  cause  each  of  its
            Subsidiaries to, permit any person designated by any Lender to visit
            and inspect any of its  properties,  corporate  books and  financial
            records, to make copies and take extracts therefrom,  and to discuss
            its accounts,  affairs,  and finances with the principal officers of
            the Company and such Subsidiary  during  reasonable  business hours,
            all at such times as the Lenders may reasonably  request;  provided,
            however,  that any time following the occurrence and  continuance of
            an Event  of  Default,  no  prior  notice  to the  Company  and such
            Subsidiary  shall be required.  The Company  shall,  and shall cause
            each of its  Subsidiaries  to,  prepare or cause to be prepared  its
            interim  statements and reports in accordance with GAAP,  subject to
            usual and  customary  year end audit and  adjustments  and  footnote
            disclosures.

                        (b) The  Company  shall,  and  shall  cause  each of its
            Subsidiaries  to,  permit  any  person  designated  by the  Agent to
            conduct  field audits of all accounts  receivable of the Company and
            each of its Subsidiaries as any Lender may reasonably request at any
            time and from time to time, such field audits to be conducted at the
            expense of the Company no more frequently  than annually,  unless an
            Event of Default has occurred and is continuing,  at which time such
            field  audits  shall be  conducted  at the expense of the Company as
            frequently as any Lender shall request."

            e.  Section  6.09 of the  Credit  Agreement  is  hereby  amended  by
replacing clause (a) of Section 6.09 in its entirety with the following:

                        "(a) In any  fiscal  year of the  Company,  the  Company
            shall not pay or declare  any cash  dividends  on any of its capital
            stock;  provided,  however, the Company may accrue and cumulate, but
            not pay, cash dividends on the 8% Convertible Preferred Stock."

            f.  Section  7.01 of the  Credit  Agreement  is  hereby  amended  by
replacing such Section 7.01 in its entirety with the following:

                        "SECTION  7.01 Senior Debt Coverage  Ratio.  The Company
            shall not permit the Senior Debt  Coverage  Ratio as of the last day
            of any fiscal  quarter of the Company to be greater than (i) 3.35 to
            1.00 for the period beginning on April 1, 2000 through and

                                       4

<PAGE>

            including June 30, 2000; (ii) 3.25 to 1.00 for the period  beginning
            July 1, 2000 through and including September 30, 2000; (iii) 3.05 to
            1.00 for the period beginning  October 1, 2000 through and including
            December  31,  2000;  (iv)  2.90 to 1.00  for the  period  beginning
            January 1, 2001 through and  including  March 31, 2001;  (v) 2.75 to
            1.00 for the period  beginning  April 1, 2001 through and  including
            June 30, 2001;  (vi) 2.60 to 1.00 for the period  beginning  July 1,
            2001 through and  including  September  30, 2001;  and (vii) 2.50 to
            1.00 thereafter."

            g.  Section  7.02 of the  Credit  Agreement  is  hereby  amended  by
replacing such Section 7.02 in its entirety with the following:

                        "SECTION 7.02 Interest Coverage Ratio. The Company shall
            not permit the ratio of the last  twelve  months  EBITDA to the last
            twelve  months  Interest  Expense  as of the last day of any  fiscal
            quarter  of the  Company  to be less  than  (i) 1.40 to 1.00 for the
            period  beginning  on April 1, 2000 through and  including  June 30,
            2000;  (ii)  1.50 to 1.00  for the  period  beginning  July 1,  2000
            through and including September 30, 2000; (iii) 1.60 to 1.00 for the
            period  beginning  October 1, 2000 through and  including  March 31,
            2001;  (iv)  1.75 to 1.00 for the  period  beginning  April 1,  2001
            through and including June 30, 2001; (v) 1.95 to 1.00 for the period
            beginning  July 1, 2001 through and  including  September  30, 2001;
            (vi) 2.40 to 1.00 for the period  beginning  October 1, 2001 through
            and including  December 31, 2001;  (vii) 2.50 to 1.00 for the period
            beginning  January 1, 2002 through and including March 31, 2002; and
            (viii) 2.75 to 1.00 thereafter."

            h.  Section  7.03 of the  Credit  Agreement  is  hereby  amended  by
replacing such Section 7.03 in its entirety with the following:

                        "SECTION  7.03 Total  Funded Debt  Coverage  Ratio.  The
            Company shall not permit the Total Funded Debt Coverage  Ratio as of
            the last day of any fiscal quarter of the Company to be greater than
            (i) 5.75 to 1.00 for the period  beginning  on April 1, 2000 through
            and  including  June 30,  2000;  (ii)  5.35 to 1.00  for the  period
            beginning  July 1, 2000 through and  including  September  30, 2000;
            (iii) 5.00 to 1.00 for the period beginning  October 1, 2000 through
            and  including  December 31, 2000;  (iv) 4.75 to 1.00 for the period
            beginning  January 1, 2001 through and including March 31, 2001; (v)
            4.50 to 1.00 for the  period  beginning  April 1, 2001  through  and
            including June 30, 2001; and (vi) 4.25 to 1.00 thereafter."

            i.  Section  7.04 of the  Credit  Agreement  is  hereby  amended  by
replacing such Section 7.04 in its entirety with the following:

                        "SECTION  7.04 Minimum Net Worth.  The Company  shall at
            all times  maintain  its  Consolidated  Net Worth  greater  than the
            Minimum Net Worth, equal to (i) $40,000,000, plus (ii) fifty percent
            (50%) of the  cumulative  Consolidated  Net Income  for each  fiscal
            quarter  beginning after the fiscal quarter ending on March 31, 2000
            (specifically not including any Consolidated Net Loss for any fiscal
            quarter),  plus  (iii) the  cumulative  net  proceeds  of all equity
            offerings, except for the 8% Convertible Preferred Stock."

                                       5

<PAGE>

            j.  Section 8.01 of the Credit  Agreement  is hereby  amended (i) to
delete the  punctuation  "." at the end of clause (o) thereof and to  substitute
therefor  the new language "; or" and (ii) to add the  following  new clause (p)
thereto:

                        "(p) The Company's  aggregate  outstanding  Advances and
Letters of Credit under this Agreement exceed the Borrowing Base."

            k. Annex A of the Credit  Agreement  is hereby  amended by replacing
such  Annex A in its  entirety  with the Annex A  attached  hereto as Exhibit A.

            2. Conditions Precedent.  This Amendment shall become effective upon
satisfaction of the following conditions:

            a.  The  Agent  shall  have  received  one  or  more  duly  executed
counterparts of this Amendment signed by each of the parties hereto.

            b. The Agent shall have  received a copy of the Fifth  Amendment  to
Senior  Subordinated  Debt, in substantially the form attached hereto as Exhibit
A, as executed by the parties  thereto.  The terms and  conditions of such Fifth
Amendment to Senior  Subordinated  Debt shall be satisfactory in all respects to
the Agent.

            c. The Agent shall have received such other  documents as any Lender
may reasonably request.

            3. Other Agreements.

            a. For purposes of clarity,  the Company,  the Agent and the Lenders
hereby  acknowledge  and agree  that the  Company  may  furnish to the Agent for
distribution to each of the Lenders a revised Borrowing Base Certificate for the
month ending March 31, 2000 in accordance  with the terms and  conditions of the
Credit Agreement as amended hereby.

            b. The Company hereby affirms that each of the  representations  and
warranties  of the Company  contained in the Credit  Agreement  and in any other
Loan Documents  (except to the extent that any such  representation  or warranty
expressly relates solely to an earlier date and for changes therein permitted or
contemplated by the Credit Agreement) is correct in all material respects on and
as of the date hereof and after giving  effect to this  Amendment.  In addition,
with  respect  to this  Amendment,  Company  warrants  and  represents  that the
execution,  delivery and performance by Company of this Amendment (i) are within
the Company's  corporate power;  (ii) have been duly authorized by all necessary
or proper corporate  action;  (iii) are not in contravention of any provision of
the Company's  certificate of incorporation or bylaws; (iv) will not violate any
law or regulation,  or any order or decree of any  Governmental  Authority;  (v)
will not conflict with or result in the breach or termination  of,  constitute a
default  under  or  accelerate  any  performance  required  by,  any  indenture,
mortgage,  deed of trust,  lease,  agreement  or other

                                       6

<PAGE>

instrument to which the Company is a party or by which the Company or any of its
property is bound;  (vi) will not result in the  creation or  imposition  of any
Lien upon any of the  property of the  Company  other than those in favor of the
Agent for the benefit of the Lenders,  all pursuant to the Loan  Documents;  and
(vii) do not require the  consent or  approval  of any  Governmental  Authority.
Company  further  represents  and  warrants  that this  Amendment  has been duly
executed  and  delivered  for the  benefit  of or on behalf of the  Company  and
constitutes a legal,  valid and binding  obligation of the Company,  enforceable
against the Company in accordance with its terms.

            c. As  amended  hereby,  all terms of the Credit  Agreement  and the
other  Loan  Documents  shall be and  remain in full  force and effect and shall
constitute the legal, valid, binding and enforceable  obligations of the Company
to the Agent and the  Lenders.  To the  extent any terms and  conditions  in any
other  Loan  Documents  shall  contradict  or be in  conflict  with any terms or
conditions of the Credit Agreement,  after giving effect to this Amendment, such
terms and  conditions  are hereby  deemed  modified and amended  accordingly  to
reflect the terms and conditions of the Credit Agreement as modified and amended
hereby.

            d. The Company  hereby  restates,  ratifies and  reaffirms  each and
every term and  condition  set forth in the Credit  Agreement and the other Loan
Documents,  effective as of the date hereof,  and represents  that, after giving
effect to this  Amendment,  no Default or Event of Default has  occurred  and is
continuing as of the date hereof.

            e. The Company agrees to pay on demand all costs and expenses of the
Agent in connection with the preparation, execution, delivery and enforcement of
this Amendment,  the closing  hereof,  and any other  transactions  contemplated
hereby, including the fees and out-of-pocket expenses of the Company's counsel.

            f. This  Amendment  may be executed  in any number of  counterparts,
each of which  shall be deemed an  original  and all of which,  taken  together,
shall constitute one and the same instrument.

            g. THIS AMENDMENT  SHALL BE GOVERNED BY, AND CONSTRUED IN ACCORDANCE
WITH THE INTERNAL LAWS (AND NOT THE LAWS OF CONFLICTS),  OF THE STATE OF FLORIDA
AND ALL APPLICABLE LAWS OF THE UNITED STATES OF AMERICA.

                  (Remainder of Page Intentionally Left Blank)

                                       7

<PAGE>

           IN WITNESS WHEREOF, the parties hereto have caused this Amendment to
be duly  executed  under  seal  by  their  respective  officers  thereunto  duly
authorized, as of the date first above written.

                                      NUCO2 INC.,
                                      a Florida corporation

                                      By: /s/ Joann Schirripa
                                          -------------------------------------
                                          Joann Schirripa
                                          Chief Financial Officer and Treasurer

                                      Attest: /s/ Eric M. Wechsler
                                              ---------------------------------
                                              Eric M. Wechsler
                                              General Counsel and Secretary

<PAGE>
                                       SUNTRUST BANK
                                       individually and as Agent
                                       By: /s/ Russell E. Burnette
                                           ------------------------------------
                                             Russell E. Burnette
                                             Vice President

                                       BANK AUSTRIA CREDITANSTALT
                                       CORPORATE FINANCE, INC.,
                                       individually and as Documentation Agent

                                       By: /s/ Scott Kray
                                           ------------------------------------
                                             Name: Scott Kray
                                             Title: Vice President

                                       By: /s/ Gary W. Andresen
                                           ------------------------------------
                                             Name: Gary W. Andresen
                                             Title: Senior Associate

                                       BANK-LEUMI LE-ISRAEL B.M.,
                                       MIAMI AGENCY
                                       By: /s/ Stephen Hanas
                                           ------------------------------------
                                             Stephen Hanas
                                             Vice President

                                       THE PROVIDENT BANK
                                       By: /s/ Nick Jevic
                                           ------------------------------------
                                             Nick Jevic
                                             Vice President

                                       IBJ WHITEHALL BUSINESS CREDIT
                                       CORPORATION
                                       By: /s/ Edward A. Jesser
                                           ------------------------------------
                                             Edward A. Jesser
                                             Sr. Vice President

                                       HAMILTON BANK, N.A.

                                       By: /s/ Hector F. Ramirez
                                           ------------------------------------
                                             Name: Hector F. Ramirez
                                             Title: Senior Vice President

                                       By: /s/ Emilio R. Rangel Jr.
                                           ------------------------------------
                                             Name: Emilio R. Rangel Jr.
                                             Title: Assistant Vice President

<PAGE>

                          ACKNOWLEDGMENT OF GUARANTORS

            Each of the Guarantors  acknowledges  and agrees to the terms of the
foregoing Second Amendment to Amended and Restated  Revolving Credit  Agreement,
and  further  acknowledges  and agrees  that (i) all of the  obligations  of the
Company shall  continue to constitute  "Guaranteed  Obligations"  covered by the
Amended and Restated Guaranty  Agreement dated as of May 4, 1999 executed by the
undersigned,  and (ii) the Amended and Restated Guaranty  Agreement is and shall
remain in full  force and  effect  on and after the date  hereof,  and (iii) the
foregoing agreement shall in no way release,  discharge,  or otherwise limit the
obligations of such Guarantor under the Amended and Restated Guaranty Agreement.

            This  Acknowledgment  of  Guarantors is made and delivered as of May
12, 2000.

                                       GUARANTORS:

                                       NUCO2 ACQUISITION CORP.,
                                       a Florida corporation

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

                                       [CORPORATE SEAL]

                                       KOCH COMPRESSED GASES, INC.,
                                       a New Jersey corporation

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

                                       [CORPORATE SEAL]

<PAGE>

                                    EXHIBIT A

                                     ANNEX A

            Date                                          Projected Gross Margin

March 2000                                                          49.90%

April 2000                                                          50.20%

May 2000                                                            50.50%

June 2000                                                           50.80%

July 2000                                                           50.80%

August 2000                                                         51.20%

September 2000                                                      51.60%

October 2000                                                        51.70%

November 2000                                                       52.30%

December 2000                                                       52.70%

January 2001                                                        53.30%

February 2001                                                       53.70%

March 2001                                                          54.20%

April 2001                                                          54.60%

May 2001                                                            55.10%

June 2001                                                           55.50%

July 2001                                                           55.80%

August 2001                                                         56.10%

September 2001                                                      56.40%

<PAGE>
            Date                                          Projected Gross Margin

October 2001                                                        56.70%

November 2001                                                       57.00%

December 2001                                                       57.20%

January 2002                                                        57.60%

February 2002                                                       57.80%

March 2002                                                          58.10%Exhibit 10.15

                                 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:

<PAGE>

                                      -2-

            "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

            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

<PAGE>
                                      -3-

            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)  $37,500,000,  (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 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.

<PAGE>

            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: CFO

                                   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

<PAGE>

                                   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 - Mezzanine

                                   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

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