Void after 5:00 p.m.Eastern Standard Time, on May 15, 2010. Warrant to Purchase 40,000 Shares of Common Stock.

EXHIBIT 4.1

THE ISSUANCE OF THIS WARRANT AND THE OFFER AND SALE OF THE SHARES OF COMMON STOCK ISSUABLE HEREUNDER HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 (THE “ACT”) NOR UNDER ANY STATE SECURITIES LAW AND THIS WARRANT AND ANY SUCH SHARES OF COMMON STOCK MAY NOT BE PLEDGED, SOLD, ASSIGNED OR OTHERWISE TRANSFERRED UNTIL A (1) REGISTRATION STATEMENT UNDER THE ACT AND ANY APPLICABLE STATE SECURITIES LAW HAS BECOME EFFECTIVE WITH RESPECT THERETO, OR (2) RECEIPT BY THE COMPANY OF AN OPINION OF COUNSEL ACCEPTABLE TO THE COMPANY (IF SO REQUESTED) TO THE EFFECT THAT REGISTRATION UNDER THE ACT OR APPLICABLE STATE SECURITIES LAW IS NOT REQUIRED IN CONNECTION WITH THE PROPOSED TRANSFER.

Void after 5:00 p.m. Eastern Standard Time, on May 15, 2010.

Warrant to Purchase 40,000 Shares of Common Stock.

WARRANT TO PURCHASE COMMON STOCK

OF

ALLION HEALTHCARE, INC.

This is to certify that, for good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, Crestview Capital Master, LLC (“Holder”) is entitled to purchase, subject to the provisions of this Warrant, from Allion Healthcare, Inc., a Delaware corporation (“Company”), forty thousand (40,000) fully paid, validly issued and nonassessable shares of Common Stock, $0.01 par value per share, of the Company (“Common Stock”) at a price per share initially set at the IPO Price (as defined below) at any time or from time to time during the period from IPO Date (as defined below) to expiration, but not later than 5:00 p.m. Eastern Standard Time, on May 15, 2010. The number of shares of Common Stock issuable upon exercise of this Warrant shall increase by five thousand (5,000) shares per each 30 days that the IPO Date is delayed beyond November 15, 2005, but shall not be increased beyond seventy thousand (70,000) shares in total. The number of shares of Common Stock to be received upon the exercise of this Warrant and the price to be paid for each share of Common Stock may be adjusted from time to time as hereinafter set forth. The shares of Common Stock deliverable upon such exercise, and as adjusted from time to time, are hereinafter sometimes referred to as “Warrant Shares” and the exercise price of a share of Common Stock in effect at any time and as adjusted from time to time is hereinafter sometimes referred to as the “Exercise Price”. The “IPO Date” shall mean the closing date of any underwritten public offering of any shares of the Company’s capital stock resulting in aggregate proceeds to the Company in excess of $25 million, and the “IPO Price” shall mean the price per share to the public in such public offering.

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hereof. The term “Warrant” as used herein includes any Warrants into which this Warrant may be divided or exchanged. Upon receipt by the Company of evidence satisfactory to it of the loss, theft, destruction or mutilation of this Warrant, and (in the case of loss; theft or destruction) of reasonably satisfactory indemnification, and upon surrender and cancellation of this Warrant, if mutilated, the Company will execute and deliver a new Warrant of like tenor and date. Any such new Warrant executed and delivered shall constitute an additional contractual obligation on the part of the Company, whether or not this Warrant so lost, stolen, destroyed, or mutilated shall be at any time enforceable by anyone.

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so offered) would purchase at the Exercise Price in effect immediately prior to the date of such issuance, and the denominator of which shall be the sum of the number of shares of Common Stock outstanding on the record date mentioned above and the number of additional shares of Common Stock offered for subscription or purchase (or into which the convertible securities so offered are convertible). Such adjustment shall be made successively whenever such rights or warrants are issued and shall become effective immediately after the record date for the determination of shareholders entitled to receive such rights or warrants; and to the extent that shares of Common Stock are not delivered (or securities convertible into Common Stock are not delivered) after the expiration of such rights or warrants, the Exercise Price shall be readjusted to the Exercise Price which would then be in effect had the adjustments made upon the issuance of such rights or warrants been made upon the basis of delivery of only the number of shares of Common Stock (or securities convertible into Common Stock) actually delivered.

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for the issuance of such securities plus the additional minimum consideration, if any, to be received by the Company upon the conversion or exchange thereof the consideration in each case to be determined in the same manner as provided in clauses (A) and (B) of this Subsection (5).

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forthwith file, in the custody of its Secretary or an assistant Secretary at its principal office and with its stock transfer agent, if any, an officer’s certificate showing the adjusted Exercise Price determined as herein provided, setting forth in reasonable detail the facts requiring such adjustment, including a statement of the number of additional shares of Common Stock, if any, and such other facts as shall be necessary to show the reason for and the manner of computing such adjustment. Each such officer’s certificate shall be made available at all reasonable times for inspection by the Holder or any holder of a Warrant executed and delivered pursuant to Section (a).

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provision shall include provision for adjustments which shall be as nearly equivalent as may be practicable to the adjustments provided for in this Warrant. The foregoing provisions of this Section (i) shall similarly apply to successive reclassifications, capital reorganizations and changes of shares of Common Stock and to successive consolidations, mergers, sales or conveyances. In the event that in connection with any such capital reorganization or reclassification, consolidation, merger, sale or conveyance, additional shares of Common Stock shall be issued in exchange, conversion, substitution or payment, in whole or in part, for a security of the Company other than Common Stock, any such issue shall be treated as an issue of Common Stock covered by the provisions of Subsection (1) of Section (f) hereof.

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Dated:                     

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PURCHASE FORM

Dated                             

The undersigned hereby irrevocably elects to exercise the within Warrant to the extent of purchasing              shares of Common Stock and hereby makes payment of              in payment of the actual exercise price thereof. In lieu of payment of the actual exercise price, the undersigned may direct the Company to net issue such shares of Common Stock in accordance with Section (a)(2) of the within Warrant by writing “net issue” in the space after “payment” of in the preceding sentence.

INSTRUCTIONS FOR REGISTRATION OF STOCK

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ASSIGNMENT FORM

FOR VALUE RECEIVED;                      hereby sells, assigns and transfers unto

the right to purchase Common Stock represented by this Warrant to the extent of              shares as to which such right is exercisable and does hereby irrevocably constitute and appoint                      attorney, to transfer the same on the books of the Company with full power of substitution in the premises.

Date                    , 200  

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