EXHIBIT 99.4
 
                         NOTICE OF GUARANTEED DELIVERY
                                   TO TENDER
              UNREGISTERED 13% SENIOR DISCOUNT DEBENTURES DUE 2009
                      (INCLUDING THOSE IN BOOK-ENTRY FORM)
                                       OF
                               MEDIQ INCORPORATED
 
      PURSUANT TO THE EXCHANGE OFFER AND PROSPECTUS DATED           , 1998
 
    As set forth in the Prospectus (as defined below), this form or one
substantially equivalent hereto must be used to accept the Exchange Offer (as
defined below) if certificates for unregistered 13% Senior Discount Debentures
due 2009 (the "Old Debentures") of MEDIQ Incorporated are not immediately
available or time will not permit a holder's Old Debentures or other required
documents to reach the Exchange Agent (as defined below) on or prior to the
Expiration Date (as defined below), or the procedure for book-entry transfer
cannot be completed on a timely basis. This form may be delivered by facsimile
transmission, by registered or certified mail, by hand, or by overnight delivery
service to the Exchange Agent. See "THE EXCHANGE OFFERS--Procedures for
Tendering" in the Prospectus.
 
THE EXCHANGE OFFER FOR THE OLD DEBENTURES (THE "EXCHANGE OFFER") AND WITHDRAWAL
RIGHTS WILL EXPIRE AT 5:00 P.M., NEW YORK CITY TIME, ON           , 1998 ("THE
EXPIRATION DATE"), UNLESS THE EXCHANGE OFFER IS EXTENDED BY THE COMPANY.
 
                 THE EXCHANGE AGENT FOR THE EXCHANGE OFFER IS:
                    UNITED STATES TRUST COMPANY OF NEW YORK
 

                                                        
  BY OVERNIGHT COURIER AND                BY HAND              BY REGISTERED OR CERTIFIED
    BY HAND AFTER 4:30 PM             UP TO 4:30 PM:                      MAIL:
ON THE EXPIRATION DATE ONLY:
 
 United States Trust Company    United States Trust Company    United States Trust Company
         of New York                    of New York                    of New York
  770 Broadway, 13th Floor             111 Broadway                   P.O. Box 844
  New York, New York 10003              Lower Level                  Cooper Station
    Attn: Corporate Trust        New York, New York 10006     New York, New York 10276-0844
          Services                 Attn: Corporate Trust          Attn: Corporate Trust
                                         Services                       Services
                                 Telephone: (800) 548-6565
                                 Facsimile: (212) 780-0592
                                      (212) 420-6211

 
    (Originals of all documents sent by facsimile should be sent promptly by
                         registered or certified mail,
                  by hand, or by overnight delivery service.)

   DELIVERY OF THIS NOTICE TO AN ADDRESS OR TRANSMISSION OF INSTRUCTIONS VIA
 FACSIMILE OTHER THAN AS SET FORTH ABOVE WILL NOT CONSTITUTE A VALID DELIVERY.

Ladies and Gentlemen:
 
    The undersigned hereby tenders to MEDIQ Incorporated, a Delaware corporation
(the "Company"), in accordance with the Company's offer, upon the terms and
subject to the conditions set forth in the Prospectus dated           , 1998
(the "Prospectus"), and in the accompanying Letter of Transmittal, receipt of
which is hereby acknowledged, $      in aggregate principal amount at maturity
of Old Debentures pursuant to the guaranteed delivery procedures described in
the Prospectus.
 
Name(s) of Registered Holder(s):
 
________________________________________________________________________________
                             (Please Type or Print)
 
Address: _______________________________________________________________________
 
________________________________________________________________________________
 
Area Code & Telephone No: ______________________________________________________
 
Certificate Number(s) for
Old Debentures (if available): _________________________________________________
 
Total Principal Amount at Maturity
Tendered and Represented
by Certificate(s): $ ___________________________________________________________
 
Signature of Registered Holder(s): _____________________________________________
 
Dated: _________________________________________________________________________
 
/ / The Depository Trust Company
  (Check if Old Debentures will be tendered
  by book-entry transfer)
 
Account Number: ________________________________________________________________

                     THE GUARANTEE BELOW MUST BE COMPLETED
 
                                   GUARANTEE
                    (NOT TO BE USED FOR SIGNATURE GUARANTEE)
 
    The undersigned, being a member of or participant in the Securities Transfer
Agents Medallion Program, the New York Stock Exchange Medallion Signature
Program or the Stock Exchange Medallion Program or an "eligible guarantor
institution" within the meaning of Rule 17Ad-15 under the Securities Exchange
Act of 1934, as amended (the "Exchange Act"), hereby guarantees (a) that the
above named person(s) "own(s)" the Old Debentures tendered hereby within the
meaning of Rule 14e-4 under the Exchange Act ("Rule 14e-4"), (b) that such
tender of such Old Debentures complies with Rule 14e-4 and (c) to deliver to the
Exchange Agent the certificates representing the Old Debentures tendered hereby
or confirmation of book-entry transfer of such Old Debentures into the Exchange
Agent's account at The Depository Trust Company, in proper form for transfer,
together with a Letter of Transmittal (or facsimile thereof), properly completed
and duly executed, with any required signature guarantees and any other required
documents, within three New York Stock Exchange trading days after the earlier
of (i) the date of execution hereof and (ii) the Expiration Date.
 
Name of Firm: __________________________________________________________________
 
Address: _______________________________________________________________________
 
________________________________________________________________________________
 
Area Code and Telephone No.: ___________________________________________________
 
Authorized Signature: __________________________________________________________
 
Name: __________________________________________________________________________
 
Title: _________________________________________________________________________
 
Dated: _________________________________________________________________________
 
NOTE: DO NOT SEND CERTIFICATES OF OLD DEBENTURES WITH THIS FORM. CERTIFICATES OF
      OLD DEBENTURES SHOULD BE SENT ONLY WITH A PROPERLY COMPLETED AND DULY
      EXECUTED LETTER OF TRANSMITTAL.