EXHIBIT 4


THIS DEBENTURE, AND THE SHARES OF COMMON STOCK ISSUABLE UPON CONVERSION HEREOF,
HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR
APPLICABLE STATE SECURITIES LAWS AND MAY NOT BE REOFFERED OR SOLD, TRANSFERRED,
PLEDGED, HYPOTHECATED OR OTHERWISE DISPOSED OF, EXCEPT PURSUANT TO (l)
REGISTRATION OR (2) AN OPINION OF COUNSEL FOR THE COMPANY OR OTHER COUNSEL
REASONABLY ACCEPTABLE TO THE COMPANY TO THE EFFECT THAT SUCH REGISTRATION IS NOT
REQUIRED.


$504,040.00                                                       July 30 , 1998
                                                          Minneapolis, Minnesota


                     11% SUBORDINATED CONVERTIBLE DEBENTURE


         For good and valuable consideration, the receipt of which is hereby
acknowledged, the undersigned, Venturian Corp., a Minnesota corporation
("Venturian"), agrees to pay to the order of Quarterdeck Public Equities, LLC, a
Delaware limited liability company or its registered assigns ("Holder") at 10100
Santa Monica Boulevard, Suite 1425, Los Angeles, CA 90067, Attention: Jon B.
Kutler or such other address provided to Venturian by written notice, the
principal sum of Five Hundred Four Thousand Forty Dollars ($504,040.00), on July
30, 2002, with interest from the date hereof, computed at an annual percentage
rate of eleven percent (11%) on the unpaid principal balance of this Debenture.
Interest is payable on January 1, April 1, July 1 and October 1 of each year
commencing October 1, 1998; provided that interest payable on principal amounts
converted pursuant to Section 3 hereof shall be payable on the date of such
conversion. Principal and interest of this Debenture shall be payable in lawful
money of the United States of America remitted by wire transfer of immediately
available funds to such account as the Holder may hereafter designate for such
payment at the request of Venturian. Interest will be computed for the actual
number of days elapsed on the basis of a 360-day year consisting of twelve
30-day months. Interest shall accrue from the most recent date to which interest
has been paid or, if no interest has been paid, from the date of original
issuance of this Debenture. The following additional terms, covenants,
statements of holders' rights and conditions shall apply to this Debenture:

         1. No Prepayment by Venturian. The principal of this Debenture shall
not be subject to prepayment without the prior written consent of the Holder.



                                       1
<PAGE>


         2. Events of Default and Subordination.

            (a) Events of Default. The occurrence of any of the following
         events shall be an "Event of Default" under this Debenture:

                i) Nonpayment. Venturian shall fail to pay, on or before the 
            earlier of (i) five (5) business days after the date when due and
            (ii) one (1) business day after notice from Holder of Venturian's
            failure to pay when due, any principal, interest, or other amounts
            payable hereunder;

                ii) Bankruptcy or Insolvency. (i) Venturian shall become 
            insolvent, or shall suffer or consent to or apply for the
            appointment of a receiver, trustee, custodian, liquidator or other
            officer with similar powers to take possession of all or a
            substantial portion of its property or operate all or a substantial
            portion of its business or any of its property, or shall generally
            fail to pay its debts as they become due, or Venturian shall admit
            in writing its inability to pay its debts as they become due, or
            shall make a general assignment for the benefit of creditors; or
            (ii) Venturian shall file a voluntary petition in bankruptcy, or
            seeking reorganization, in order to effect a plan or other
            arrangement with creditors or any other relief under the Bankruptcy
            Reform Act, Title 11 of the United States Code, as amended or
            recodified from time to time (the "Bankruptcy Code"), or under any
            state or federal law granting relief to debtors, whether now or
            hereafter in effect (or the board of directors shall adopt any
            resolution or otherwise authorize action to approve any of the
            foregoing); or (iii) any involuntary petition or proceeding pursuant
            to the Bankruptcy Code or any other applicable state or federal law
            relating to bankruptcy, reorganization or other relief for debtors
            is filed or commenced against Venturian, and any of the following
            events occurs: (1) the petition commencing the involuntary case is
            not contested by an appropriate proceeding promptly instituted and
            diligently prosecuted, (2) the petition commencing the involuntary
            case is not stayed or dismissed within sixty (60) days after the
            petition commencing such case was filed, (3) Venturian shall file an
            answer admitting the jurisdiction of the court and the material
            allegations of any such involuntary petition or (4) Venturian shall
            be adjudicated a bankrupt, or an order for relief shall be entered
            by any court of competent jurisdiction under the Bankruptcy Code or
            any other applicable state or federal law relating to bankruptcy,
            reorganization or other relief for debtors.

                iii) Dissolution or Liquidation. Venturian shall dissolve or 
            liquidate, or there shall be commenced an action for the involuntary
            dissolution of any such entity which is not contested by an
            appropriate proceeding promptly instituted and diligently
            prosecuted.



                                       2
<PAGE>


            (b) Remedies. Upon the occurrence of an Event of Default:

                i) Termination. If an Event of Default occurs and is continuing,
            other than under Section 2(a)(ii) or (iii) (to the extent that there
            occurs a liquidation or dissolution of Venturian), the Holder may,
            effectively immediately upon written notice to Venturian, declare
            the unpaid principal amount of this Debenture to be, and the same
            shall thereupon become, due and payable, together with any and all
            accrued interest thereon and all costs payable pursuant to this
            Debenture without presentment, demand, protest, diligence, any
            additional notice whatsoever or other requirements of any kind, all
            of which are hereby expressly waived by Venturian, except as
            otherwise required by applicable law.

                ii) Enforcement. Upon the occurrence of any Event of Default and
            while such Event of Default is continuing, Holder, without notice to
            or demand upon Venturian, which are hereby expressly waived by
            Venturian, may proceed to protect, exercise and enforce its rights
            and remedies under this Debenture against Venturian, and such other
            rights and remedies as are provided by law or equity. Such
            proceedings may take place either by suit in equity or by action at
            law, or both, and may be for specific performance of any covenant or
            agreement contained in this Debenture or in the aid of the exercise
            of any power granted in this Debenture. No remedy conferred in this
            Debenture upon the holder of this Debenture is intended to be
            exclusive of any other remedy, and each and every such remedy shall
            be cumulative and shall be in addition to every other remedy
            conferred herein or now or otherwise existing at law or in equity,
            or by statute or otherwise.

            (c) No Security; Subordination. This Debenture is not secured by any
collateral nor is it the subject of any guaranty. Payment of the principal and
interest on this Debenture is expressly subordinate to all indebtedness of
Venturian for money borrowed from any bank, trust company, insurance company,
mortgage company, leasing company or other institutional lender outstanding on
the date of the execution of this Debenture and any extension, renewal or
replacement thereof and any additional indebtedness of Venturian hereafter
created or incurred for money borrowed from any such institutional lender,
provided that the instrument evidencing such additional indebtedness designates
such indebtedness as senior debt of the kind contemplated hereby. The provisions
of this Section 2(c) are intended solely for the purpose of defining the rights
inter se of the Holder, on the one hand, and the holders of senior debt, on the
other. Nothing in this Agreement is intended to or shall (i) in any way impair,
as between the Holder and Venturian's creditors other than the holders of senior
debt, Venturian's absolute and unconditional obligation to pay the principal and
interest of this Debenture as and when it shall become due and payable in
accordance with its terms, or (ii) affect the relative rights against Venturian
of the Holder and Venturian's creditors other than the holders of senior debt,
or (iii) if an Event of Default occurs, prevent Holder from exercising all
remedies available to it under this agreement and applicable law, subject only
to the rights of the holders of senior debt.



                                       3
<PAGE>



         3. Conversion into Common Stock.

            (a) At any time during the Conversion Period (as defined below), 
         Holder may, at its option, by written notice (the "Conversion Notice")
         delivered, mailed (registered or certified mail, postage prepaid), or
         by facsimile transmission (if followed by original delivered or
         received by registered or certified mail, postage prepaid, within five
         business days after the facsimile transmission) to Venturian at its
         principal office, elect to convert all or any part of the entire
         outstanding principal amount of this Debenture into shares of Venturian
         common stock, $1.00 par value per share ("Common Stock"), at a price of
         $8.00 per share (as adjusted pursuant to Section 6 below, the
         "Conversion Price"). The Conversion Notice shall be accompanied by
         instructions specifying the name or names in which the shares of stock
         deliverable upon such conversion shall be registered, along with the
         addresses of the persons so named and, if required by Venturian,
         accompanied by a written instrument of transfer in form satisfactory to
         Venturian duly executed by Holder. The Conversion Period shall commence
         on November 27, 1998 (120 days from the date of original issuance of
         this Debenture) and expire on the third anniversary of the date of
         original issuance of this Debenture (the "Original Issuance Date").

            (b) At any time on or after the third anniversary of the Original 
         Issuance Date, Venturian may, at its option, by written notice (the
         "Venturian Conversion Notice") delivered, mailed (registered or
         certified mail, postage prepaid), or by facsimile transmission (if
         followed by original delivered or received by registered or certified
         mail, postage prepaid, within five business days after the facsimile
         transmission) to Holder at its address appearing on page one of this
         Debenture, require the conversion of all or any part of the entire
         outstanding principal amount of this Debenture into shares of Common
         Stock at the Conversion Price in effect on the date of the Venturian
         Conversion Notice. The Venturian Conversion Notice shall specify the
         principal amount of this Debenture to be converted, the Conversion
         Price then in effect and the number of shares of Common Stock into
         which this Debenture has been converted, and shall contain instructions
         for delivery of this Debenture to Venturian. Upon receipt of the
         Venturian Conversion Notice, Holder shall promptly deliver this
         Debenture to Venturian pursuant to the instructions in the Venturian
         Conversion Notice for cancellation or recordation of the conversion
         amount as provided in Section 4 hereof. On and after the date of the
         Venturian Conversion Notice, this Debenture shall represent the right
         to receive the Common Stock as specified in the Venturian Conversion
         Notice.

         4. Common Stock Issued on Conversion. Common Stock issued on conversion
of this Debenture shall be delivered as follows:

            (a) As promptly as practicable after the surrender of this Debenture
         for conversion, Venturian shall deliver to Holder, or to such person or
         persons as designated by Holder in the Conversion Notice, a certificate
         or certificates representing the number of fully paid and nonassessable
         shares of Common Stock into which this Debenture or portion thereof is
         to be converted in the name of Holder or such name or names as are



                                       4
<PAGE>

         specified in the Conversion Notice, together with any cash payable in
         respect of a fractional share and interest accrued and payable with
         respect to the converted principal amount. The date of conversion
         ("Conversion Date") shall be the date when this Debenture shall have
         been surrendered for conversion if such conversion is pursuant to
         Section 3(a) above (or, if earlier, the date the Conversion Notice is
         delivered by facsimile transmission, if such transmission is followed,
         within five business days, by delivery or receipt by mail of the
         original of the Conversion Notice accompanied by this Debenture, as
         contemplated by Section 3(a) above) and the date of the Venturian
         Conversion Notice if this Debenture is converted pursuant to Section
         3(b) above. The person entitled to receive the shares of Common Stock
         upon conversion shall be treated for all purposes as having become the
         record holder of such shares of Common Stock on the Conversion Date.

            (b) In the event less than the entire outstanding principal balance
         on this Debenture shall be converted pursuant to Section 3(a) or 3(b),
         this Debenture shall not be surrendered for cancellation but shall have
         the fact and amount of such conversion recorded on the face of this
         Debenture by writing acknowledged by Holder and Venturian. If less than
         the entire principal balance on this Debenture is converted, the amount
         of principal converted shall be an amount which results in no
         fractional shares.

         5. Covenants of Venturian. Venturian covenants and agrees that all
shares which may be issued upon conversion of this Debenture will, upon
issuance, be duly authorized and issued, fully paid and nonassessable. Venturian
further covenants and agrees that during the period within which this Debenture
may be converted into Common Stock, Venturian will at all times have authorized,
and reserved for the purpose of issue upon conversion hereof, a sufficient
number of shares of its Common Stock to provide for the conversion of this
Debenture.

         6. Anti-dilution Adjustments. The above provisions are, however,
subject to the following:

            (a) In case Venturian shall at anytime hereafter subdivide or
         combine the outstanding shares of Common Stock or declare a dividend
         payable in Common Stock, the Conversion Price in effect immediately
         prior to the subdivision, combination or record date for such dividend
         payable in Common Stock shall forthwith be proportionately increased,
         in the case of combination, or decreased, in the case of subdivision or
         dividend payable in Common Stock.

            (b) If any capital reorganization or reclassification of the capital
         stock of Venturian, or consolidation or merger of Venturian with
         another corporation, or the sale of all or substantially all of its
         assets to another corporation shall be effected in such a way that
         holders of Common Stock shall be entitled to receive stock, securities
         or assets with respect to or in exchange for Common Stock, then, as a
         condition of such reorganization, reclassification, consolidation,
         merger or sale, lawful and adequate provision shall be made whereby the
         holder hereof shall have the right to receive upon the basis and upon
         the terms and conditions specified in this Debenture and in lieu of the



                                       5
<PAGE>

         shares of the Common Stock of Venturian into which this Debenture was
         immediately theretofore convertible, such shares of stock, securities
         or assets as may be issued or payable with respect to or in exchange
         for a number of outstanding shares of such Common Stock equal to the
         number of shares of such stock into which this Debenture was
         immediately theretofore convertible had such reorganization,
         reclassification, consolidation, merger or sale not taken place, and in
         any such case appropriate provisions shall be made with respect to the
         rights and interests of Holder to the end that the provisions hereof
         (including without limitation provisions for adjustments of the
         Conversion Price and of the number of shares into which this Debenture
         may be converted) shall thereafter be applicable, as nearly as may be,
         in relation to any shares of stock, securities or assets thereafter
         deliverable upon the conversion hereof. Venturian shall not effect any
         such consolidation, merger or sale, unless prior to the consummation
         thereof the successor corporation (if other than Venturian) resulting
         from such consolidation or merger or the corporation purchasing such
         assets shall assume by written instrument executed and mailed to the
         registered holder hereof at the last address of such holder appearing
         on the books of Venturian, the obligation to deliver to such holder
         such shares of stock, securities or assets into which, in accordance
         with the foregoing provisions, such holder may be entitled to convert
         this Debenture.

            (c) If Venturian issues or sells any shares of Common Stock for a 
         consideration per share less than the Conversion Price then in effect
         (other than dividends payable in shares of Common Stock), or issues any
         options, warrants, or other rights to purchase Common Stock at a
         consideration per share less than the Conversion Price then in effect,
         or issues securities convertible into Common Stock at a conversion
         price per share of less than the Conversion Price then in effect, then
         the Conversion Price in effect immediately prior to such issuance or
         sale shall be decreased (and shall in no event be increased, except as
         provided in the succeeding sentence) so as to equal a fraction, the
         numerator of which shall be an amount equal to the sum of (A) the
         aggregate number of shares of Common Stock outstanding immediately
         prior to such issuance or sale multiplied by the applicable Conversion
         Price in effect immediately prior to such issuance or sale, and (B) the
         total consideration payable to Venturian upon such issuance or sale of
         such Common Stock and/or such purchase rights or convertible
         securities, plus the consideration payable to Venturian upon the
         exercise of such purchase rights or upon conversion of such convertible
         securities, and the denominator of which shall be an amount equal to
         the aggregate number of shares of Common Stock outstanding immediately
         after such issuance or sale plus the number of shares of Common Stock
         issuable upon the exercise of any purchase rights and/or upon the
         conversion of convertible securities issued in such issuance. If the
         Conversion Price is decreased as the result of the issuance of any
         options, warrants or other purchase rights or upon the issuance of
         convertible securities (i) no further decrease of such conversion price
         shall be made at the time of the exercise of such options, warrants or
         other purchase rights or the conversion of such convertible securities
         so long as the purchase price for such shares issued upon exercise or
         the conversion price applicable to such conversion is not less than the
         exercise price or conversion price provided at the time of issuance of
         such options, warrants, other purchase rights or convertible
         securities, and (ii) such conversion



                                       6
<PAGE>

         price shall be increased to eliminate the effect of the decrease above
         to the extent that any such options, warrants, or other purchase rights
         or convertible securities expire prior to exercise or conversion. If
         the purchase price of shares issued hereafter is payable, in whole or
         in part, in consideration other than cash, the amount of such
         consideration other than cash received by Venturian shall be deemed,
         for purposes of this Section 6(c), to be the fair value of such
         consideration as determined by the Board of Directors of Venturian;
         provided, however, that if the Holder objects to the amount so
         determined by the Board, the valuation shall be definitively determined
         by a valuation firm mutually designated by the Board and the Holder (or
         if they are unable to agree on such valuation firm, then such valuation
         firm shall be selected from among investment banking or valuation firms
         with a national reputation by application by either party to the
         American Arbitration Association), and the valuation shall be
         determined by such mutually designated firm (or the firm so designated
         by the American Arbitration Association) applying such methodology as
         such firm determines in its absolute discretion to be appropriate. The
         fees and expenses of such firm shall be borne (i) by the Holder if the
         valuation so determined by such firm is less than or equal to the
         valuation as determined by the Board and (ii) by Venturian if the
         valuation so determined by such firm is greater than the valuation as
         determined by the Board.

            (d) Notwithstanding Section 6(c) above, no adjustment of the
         Conversion Price shall be made pursuant to Section 6(c) above in the
         case of:

                i) the granting by Venturian of stock options, and the issuance
            of shares of Common Stock upon exercise of stock options granted by
            Venturian, to Venturian's employees, officers and directors (other
            than any stock options to Gary B. Rappaport) under a plan approved
            by the Board and a majority of the outstanding shares of Common
            Stock of Venturian so long as the price at which Common Stock is
            purchased pursuant to the exercise thereof is not less than the fair
            market value of the Common Stock on the date of grant of such stock
            option and provided, however, that any options granted to any member
            of Gary Rappaport's immediate family shall be consistent in nature
            and amount with those granted to employees, officers and directors
            with similar responsibilities;

                ii) The issuance of shares of Common Stock pursuant to the 
            exercise of any options, warrants, or other rights to purchase
            Common Stock, or pursuant to the conversion of securities
            convertible into Common Stock, if such options, warrants, other
            rights or convertible securities were issued on or prior to the
            Original Issuance Date; or

                (iii) the issuance of such additional shares of Common Stock as 
            may be issuable upon the exercise of such option as a result of
            adjustment in the number of shares covered by such options for stock
            dividends, stock splits or other changes in the capitalization of
            Venturian.



                                       7
<PAGE>


            (e) Upon any adjustment of the Conversion Price, then and in each 
         such case, Venturian shall give written notice thereof, by first class
         mail, postage prepaid, addressed to the registered holder of this
         Debenture at the address of such holder as shown on the books of
         Venturian, which notice shall state the Conversion Price resulting from
         such adjustment and the increase or decrease, if any, in the number of
         shares into which this Debenture may be converted, setting forth in
         reasonable detail the method of calculation and the facts upon which
         such calculation is based.

         7. Common Stock. As used herein, the term "Common Stock" shall mean and
include Venturian's presently authorized shares of common stock and shall also
include any capital stock of any class of Venturian hereafter authorized which
shall not be limited to a fixed sum or percentage in respect of the rights of
the holders thereof to participate in dividends or in the distribution,
dissolution or winding up of Venturian.

         8. No Voting Rights. This Debenture shall not entitle the holder hereof
to any voting rights or other rights as a shareholder of Venturian.

         9. Conversion or Transfer of Debenture or Resale of Common Stock. This
Debenture, and the shares of common stock issuable upon conversion hereof, have
not been registered under the Securities Act of 1933, as amended, or applicable
state securities laws and may not be reoffered or sold, transferred, pledged,
hypothecated or otherwise disposed of, except pursuant to (1) registration under
such laws or (2) an exemption from registration under such laws. The holder of
this Debenture, by acceptance hereof, agrees to give written notice to Venturian
before converting or transferring this Debenture, in whole or in part, or
transferring any shares of Common Stock issued upon the conversion hereof, of
such holder's intention to do so, describing briefly the manner of any proposed
transfer. If the holder so elects, it may, at its own expense, include an
opinion of counsel reasonably satisfactory to Venturian that (i) the proposed
conversion or transfer may be effected without registration or qualification
under the Securities Act of 1933, as amended (the "Act") and any applicable
state securities or blue sky laws, or (ii) the proposed conversion or transfer
has been registered under such laws. If the notice is not accompanied by such an
opinion of counsel, then promptly upon receiving such written notice, Venturian
shall present copies of the written notice thereof to counsel to Venturian. If
in the opinion of such counsel the proposed conversion or transfer (i) may be
effected without registration or qualification under the Act and any applicable
state securities or blue sky laws, or (ii) has been registered under such laws,
Venturian, as promptly as practicable, not exceeding 20 days after Venturian
receives such notice, shall notify such holder of such opinion, whereupon such
holder shall be entitled to convert or transfer this Debenture or to dispose of
the shares of Common Stock received upon the previous conversion of this
Debenture, all in accordance with the terms of the notice delivered by such
holder to Venturian, provided that an appropriate legend may be endorsed on the
certificates for such shares respecting restrictions upon transfer thereof
necessary or advisable in the opinion of counsel to Venturian to prevent further
transfer which would be in violation of Section 5 of the Act and applicable
state securities or blue sky laws. No opinion of counsel to Holder or Venturian
shall be required in the case of any transfer to any member or members of Holder
or any entity in which all of the equity interests are owned by one or more
members of Holder, provided that an 




                                       8
<PAGE>

exemption from registration is available and Holder takes such action as
Venturian reasonably requests in order to comply with such exemption. If in the
opinion of counsel to Venturian or other counsel reasonably acceptable to
Venturian the proposed transfer or disposition of this Debenture or the shares
described in the written notice given pursuant to this Section 7 may not be
effected without registration of this Debenture or the shares of Common Stock
issued on the conversion hereof, Venturian shall promptly give written notice
thereof to the holder hereof not exceeding 20 days after Venturian receives such
notice, and such holder will limit its activities to such as, in the opinion of
such counsel, is permitted by law.

         10. Maximum Interest Rate; Compensation for Reduction.

            (a) Maximum Interest Rate. In no event shall the interest rate
payable with respect to this Debenture exceed the maximum rate of interest
permitted to be charged under applicable law (the "Maximum Rate"). If the amount
of interest payable for the account of the Holder on any interest payment date
would exceed the Maximum Rate, the amount of interest payable for Holder's
account on such date shall automatically be reduced to the Maximum Rate, and the
remaining amount which would otherwise have been due as interest hereunder shall
be advanced to the Holder as a non-interest-bearing loan, to be repaid at the
maturity date to the extent not repaid by application to obligations arising
under Section 10(b) below.

            (b) Compensation for Reduction. If the amount of interest payable 
for Holder's account in respect of any interest computation period hereunder is
reduced pursuant to Section 10(a) because the amount of interest payable for the
account of the Holder would exceed the Maximum Rate and the amount of interest
payable for Holder's account in respect of any subsequent interest computation
period would be less than the Maximum Rate, then the amount of interest payable
for Holder's account in respect of such subsequent interest computation period
shall be automatically increased to the Maximum Rate. Amounts due under this
Section 10 (b) shall be satisfied by the application, to the extent available,
of non-interest-bearing loans made by Venturian to the Holder under Section
10(a) hereof, and the balance shall be paid in cash.

         11. Notices. Any notice required or permitted to be given shall be
delivered or sent by certified or registered mail, addressed (a) if to the
holder of this Debenture or the shares issued upon exercise thereof, at such
holder's address as shall have been furnished by the holder to Venturian in
writing, or (b) if to Venturian, to Venturian Corp., 11111 Excelsior Boulevard,
Hopkins, MN 55343, Attention: Chief Financial Officer, or such other address as
the parties shall have furnished to the other in the manner set forth above.

         12. Miscellaneous.

            (a) Upon default in its obligations hereunder, Venturian shall pay 
         the costs, including reasonable attorneys' fees, of the holder of this
         Debenture in the pursuit of such holder's remedies hereunder.



                                       9
<PAGE>


            (b) Venturian hereby waives presentment, demand for payment, notice 
         of dishonor, and all other notices or demands in connection with the
         delivery, acceptance, performance, default or endorsement of this
         Debenture. No delay or failure on the part of Holder, its agents or
         representatives, to collect this Debenture or to exercise any power or
         right in connection with its collection shall operate as a waiver
         thereof and such rights and powers shall be deemed continuous.

            (c) No amendment, modification or waiver of any provision of this 
         Debenture shall be effective unless the same shall be in writing and
         signed by the holder hereof. No failure, delay or discontinuance on the
         part of Holder or any other holder of rights in the Debenture in
         exercising any right, power or remedy hereunder shall operate as a
         waiver thereof, nor shall any single or partial exercise of any such
         right, power or remedy preclude any other or further exercise thereof
         or the exercise of any other right, power or remedy. The remedies
         provided in this Debenture are cumulative and are not exclusive of any
         remedies that may be available to the Holder at law, in equity or
         otherwise. No amendment, modification, supplement, termination, consent
         or waiver of this Debenture, nor consent to any departure therefrom,
         shall in any event be effective unless the same shall be in writing and
         signed by Holder. Any waiver of any provision of this Debenture shall
         be effective only in the specific instance and for the specific purpose
         for which given. No notice to or demand on Venturian in any case shall
         entitle Venturian to any other or further notice or demand in similar
         or other circumstances. Any amendment, modification, termination,
         waiver or consent effected in accordance with this Section shall be
         binding upon Holder, any future Holder and Venturian. Venturian agrees
         and acknowledges that it shall not be entitled to rely upon or assert
         any purported, implied or oral modification hereof to which it is a
         party.

            (d) This Debenture shall be governed by and construed in accordance 
         with the laws of the State of Delaware.

            (e) Time is of the essence of each and every provision of this
         Debenture.

         IN WITNESS WHEREOF, the Venturian has caused this Debenture to be
signed by its authorized officers and dated as of the date stated above.


ATTEST:                                     VENTURIAN CORP.


By_______________________________           By_________________________________
    Its:_____________________________         Gary B. Rappaport
                                              Its Chief Executive Officer



                                       10