EXHIBIT 31.1


                                  CERTIFICATION

I, William F. Murdy, Chairman of the Board and Chief Executive Officer, certify
that:

1. I have reviewed this quarterly report on Form 10-Q of Comfort Systems USA,
Inc;

2. Based on my knowledge, this quarterly report does not contain any untrue
statement of a material fact or omit to state a material fact necessary to make
the statements made, in light of the circumstances under which such statements
were made, not misleading with respect to the period covered by this quarterly
report;

3. Based on my knowledge, the financial statements, and other financial
information included in this quarterly report, fairly present in all material
respects the financial condition, results of operations and cash flows of the
registrant as of, and for, the periods presented in this quarterly report;

4. The registrant's other certifying officer and I are responsible for
establishing and maintaining disclosure controls and procedures (as defined in
Exchange Act Rules 13a-15(e) and 15d-15(e)) for the registrant and we have:

a)   designed such disclosure controls and procedures, or caused such disclosure
     controls and procedures to be designed under our supervision, to ensure
     that material information relating to the registrant, including its
     consolidated subsidiaries, is made known to us by others within those
     entities, particularly during the period in which this quarterly report is
     being prepared;

b)   evaluated the effectiveness of the registrant's disclosure controls and
     procedures and presented in this quarterly report our conclusions about the
     effectiveness of the disclosure controls and procedures as of the end of
     the period covered by this quarterly report; and

c)   disclosed in this quarterly report any change in the registrant's internal
     control over financial reporting that occurred during the registrant's most
     recent fiscal quarter that has materially affected, or is reasonably likely
     to materially affect, the registrant's internal control over financial
     reporting;

5. The registrant's other certifying officer and I have disclosed, based on our
most recent evaluation of internal control over financial reporting, to the
registrant's auditors and the audit committee of registrant's board of directors
(or persons performing the equivalent function):

a)   all significant deficiencies and material weaknesses in the design or
     operation of internal controls over financial reporting which are
     reasonably

     likely to adversely affect the registrant's ability to record, process,
     summarize and report financial information; and

b)   any fraud, whether or not material, that involves management or other
     employees who have a significant role in the registrant's internal control
     over financial reporting.


Date:  August 5, 2003                            /s/ William F. Murdy
                                                 -------------------------------
                                                 William F. Murdy
                                                 Chairman of the Board and
                                                 Chief Executive Officer