the description that follows is presented to enable one skilled in the art to make and use the present invention , and is provided in the context of a particular application and its requirements . various modifications to the disclosed embodiments will be apparent to those skilled in the art , and the general principals discussed below may be applied to other embodiments and applications without departing from the scope and spirit of the invention . therefore , the invention is not intended to be limited to the embodiments disclosed , but the invention is to be given the largest possible scope which is consistent with the principals and features described herein . it will be understood that in the event parts of different embodiments have similar functions or uses , they may have been given similar or identical reference numerals and descriptions . it will be understood that such duplication of reference numerals is intended solely for efficiency and ease of understanding the present invention , and are not to be construed as limiting in any way , or as implying that the various embodiments themselves are identical . [ 0048 ] fig1 is a representative schematic drawing of the container environment 10 of the present invention . it will be understood that the container apparatus 10 would typically involve a reservoir portion 20 to contain reserve supply of volatile material 30 , such as insecticide , fragrance , other medicinal or therapeutic , etc . a “ porous ” membrane 40 is placed over the top portion of the reservoir 20 to contain the volatile material 30 . it will be understood that the temperature t 1 is room temperature in this representative system and t 0 is the temperature of the supply of the volatile material 30 remaining in the reservoir 20 of the container 10 . before use or after use , t 0 will be essentially equivalent to t 1 , i . e ., t 1 ≈ t 0 . in use , i . e ., when placed into a heating device , the container 10 will rise in themperature , and thus t 0 becomes greater . the inside surface 50 of the membrane 40 is at temperature t 1 and the outside surface 60 of the membrane 40 is at temperatue t 2 . thus , t 2 ≈ t 1 . as vaporization occurs , the membrane 40 begins to heat up , and thus both t 1 and t 2 rise above t 1 . if the membrane 40 is one of the prior art , there is a temperature gradient between the inside surface 50 of the membrane 40 at temperature t 1 and and the outer surface 60 at temperatue t 2 , in other words , t 1 & gt ; t 2 . as described above , in this case the temperature gradient is the driving mechanism behind the diffusion process . however , in the present invention , the membrane 40 is a thin film , and t 0 & gt ;& gt ; t 1 ≈ t 2 , and therefore the temperature is the determining factor in the diffusion process . [ 0051 ] fig2 shows a schematic view of a preferreed embodiment of the container 100 of the present invention . end tabs 102 are useful for inserting the container 100 into an emanator device ( shown in fig3 ). indicator film 108 covers the entire opening or upper portion of the container 100 . the device 100 has a reservoir 106 which contains the material to be volatilized 306 , i . e ., insecticidal composition , medicinal compounds or other therapeutic vapors , aromas , fragrances , etc . in a preferred embodiment , indicator film 108 is a hydrophobic film that has 35 - 55 % porosity and with pore size from 0 . 04 × 0 . 12 micron to 0 . 075 × 0 . 25 micron . the film can be heat sealed onto the metal tray . when the active ingredients is being vaporized and released through the membrane , the membrane becomes clear . the vapor of the active ingredients saturate the micro pores in the membrane and thus the film turns from opaque to clear . when the active is used up or leaves the micro pores of the membrane 108 , the film turns from clear to opaque . the present invention utilizes the containers of the prior art for containing the insecticidal or other composition 306 . in a preferred embodiment of the present invention , the containers 100 described and claimed in co - pending u . s . patent application ser . no . 09 / 870 , 115 filed may 30 , 2001 , incorporated herein by reference in its entirety , are particularly adapted for such prolonged and delayed , controlled rates of delivery of insecticidal composition 306 , medicinal compounds or other therapeutic vapors , aromas , fragrances , etc . [ 0054 ] fig3 is a representative view of a heater device apparatus 200 and environment in which a container 100 with the membrane 108 described in the current invention is used . an electrical connector 206 supplies power to an electrical resistor element ( not shown ) which causes evaporation of the active ingredient . [ 0055 ] fig4 a is a cross - sectional view of a preferred embodiment of the container 100 with the membrane 108 of the present invention prior to activation . in this view , the indicator film 108 is opaque . the indicator film membrane 108 has not been activated , and the system has not been used yet . activation can take place once the container 100 is heated for the first time . the indicator film 108 will turn from opaque to clear as the vapor of the active ingredients saturate the micro pores in the membrane 108 . [ 0056 ] fig4 b is a cross - sectional view of a preferred embodiment of the container 100 with the membrane 108 of the present invention after activation . the indicator film 108 still seals the reservior 106 which holds the volatile compostion 306 , but when the container is heated volatile material can be released .. the indicator film 108 is also still sealed to the container 100 at sealing surface 310 . in this state , the membrane 108 is transparent , translucent or clear . [ 0057 ] fig4 c is a cross - sectional view of a ptreferred embodiment of the container 100 with the membrane 108 of the present invention after all the active ingredient has been used up . the indicator film 108 has turned back from clear to opaque when the active is used up or leaves the micropores of the membrane 108 , thus indicating the depletion of the volatile composition 306 ( not shown ). in a preferred embodiment of the membrane 108 of the present invention , a semi - permeable polypropylene film is used . the trade name for this film is celgard , manufactured by celgard , division of hoechst celanese . several grades of this film can be used : celgard 2400 , 2402 , 2500 , 2502 , and 4560 . these hydrophobic films have 35 - 55 % porosity and with pore size from 0 . 04 × 0 . 12 micron to 0 . 075 × 0 . 25 micron . the film 108 can be heat sealed on to the metal tray or other portion of the container 100 . when the active ingredients are being vaporized and released through the membrane 108 , the membrane became clear . the vapor of the active ingredients saturate the micro pores in the membrane 108 and thus the film turns from opaque to clear . when the active is used up or leaves the micro pores of the membrane 108 , the film 108 turns from clear to opaque . another embodiment of this invention is using other semi - permeable films 108 including tyvek film made by dupont . this is a non - woven film made of polyethylene fiber . the film 108 has greater vapor transmission rate with noticeable change in film 108 transparency . tyvek film could serve as an on / off indicator 108 also but the change is not as dramatic as shown in celgard film . another embodiment of this invention incorporates the semi - permeable membrane 108 within a non - permeable membrane . by varying the area of the semi - permeable film 108 , the desirable release rate of active ingredients is achieved . the release of the actives can be better controlled by changing semi - permeable area size therefore maintaining a constant permeation rate through out the product cycle for different duration products . the membrane 108 also prevents evaporation of the active ingredients during non - use of the reservoir portion in an insecticide emanator device 200 . the prior art utilizes thick films , typically on the order of between about 2 mil and 400 mils , where the present invention is directed to membranes less than or equal to about 2 mils thickness . the semi - permeable film 108 can be heat sealed onto the metal tray or other portion of the container 100 . the non - permeable film is aluminum / pp or metallized pe / pet film . these films can be heat sealed onto semi - permeable films 108 . [ 0063 ] fig5 is a cross - sectional view of another preferred embodiment of the container 600 with the membrane 608 of the present invention with a protective shield member 610 of the present invention . in a preferred embodiment , the container 600 has a reservoir portion 602 which would contain the volatile material to be dispensed or diffused ( not shown ). the small - pore thin - film membrane 608 is directly adjacent the reservoir portion 602 . in this embodiment , there is a protective shield portion 610 covering the membrane 608 . small holes 612 or pores are positioned within the upper surface of the protective shield 610 to allow diffusion or transport of volatile material during use . it will be understood that this protective shield 610 is useful for controlling the temperature t 2 of the membrane 608 . it will also be understood that by establishment of the protective shield 610 shown in fig5 there is created additional geometry which may have an impact on performance thereof . in particular , while the membrane 608 may be a given distance d 1 raised above the lower surface 614 of the container 600 , the protective shielf 610 is raised a distance d 2 over the membrane 608 . furthermore , while the heater device ( not shown ) may be set at a temperature t 0 and the reservoir is maintained at a temperature t 1 , the thin - film membrane 608 will be at temperature t 2 , but the protective shield 610 may be at a lower temperature , closer to room temperature t r . therefore , it is apparent that establishing this temperature gradient , where t 0 is greater than or equal to about t 1 . t 1 may be slightly higher than or equal to t 2 , the temperature of the porous membrane 608 . finally , t 3 may be slightly higher or equal to t 2 , the temperature of the protective shield 610 . the volatile material 306 or insecticide be any one or combination of insecticides and insect repellents , and / or other active agents . particularly preferred are organic phosphorous insecticides , lipidamide insecticides , natural repellents as citronella oil , natural pyrethrins or pyrethrum extract , and synthetic pyrethroids . suitable synthetic pyrethroids are allethrin as pynamin , d - allethrin as pynamin forte , benfluthrin , bifenthrin , bioallethrin , s - bioallethrin , esbiotrin , esbiol , bioresmethrin , cycloprothrin , cyfluthrin , beta - cypermethrin , cyphenothrin , deltamethrin , empenthrin , esfenvalerate , fenpropathrin , fenvalerate , flucythrinate , tau - fluvalinate , kadethrin , permethrin , phenothrin , prallethrin as etoc , resmethrin , tefluthrin , tetramethrin , transfluthrin , or tralomethrin . fragrances 306 and / or deodorizers , such as a terpene based deodorizer fragrance may also be used in the reservoir portion 106 of the container 100 of the present invention . further , volatile fragrances , disinfectants , or other air quality modifying agents may be used , such as glycols , trimethylene , and dipropylene . in addition , organic acids that are compatible with the use of the substrate and the atmosphere can also be utilized . the following table table 1 is a listing of the vapor pressures of some of the compounds useful as active ingredients , carriers or solvents in the present invention , as well as a few compounds of the prior art with vapor pressures outside of the scope of this invention , shown for comparative purposes : it will be understood that the active ingredients or other compounds and compositions of the prior art have all been volatile at room temperature . in the present invention , the preferred embodiment contains a volatile material with a vapor pressure in the range of from about 10 − 4 torr at room temperature to about 10 − 7 torr at room temperature . in another preferred embodiment , the volatile material has a vapor pressure in the range of from about 10 − 4 torr at room temperature to about 10 − 6 torr at room temperature . other insecticidal and pesticidal compositions useful and within the scope of the present invention are described in co - pending u . s . patent application ser . no . 09 / 207 , 397 filed dec . 8 , 1998 , u . s . patent application ser . no . 09 / 666 , 716 filed sep . 20 , 2000 , and u . s . patent application ser . no . 09 / 870 , 117 filed may 30 , 2001 , all hereby incorporated herein by reference in their entireties . it will be understood that the membrane film 108 for the container 100 of the present invention operates according to various mechanisms . in a preferred embodiment , the film 108 is opaque and is effective for sealing the reservoir 106 from preventing leakage of the volatile material when not desired or not in use . when in use , i . e ., when the membrane is in use on a container device 100 such as for containing a fragrance , deodorizer or insecticides and the like and the container is placed into a heater device 200 as shown and known in the prior art , the membrane film 108 turns from opaque to clear , as a result of saturation of the membrane with the vaporized materials . in a preferred embodiment , it is one or more chemical components of the composition of the fluid or paste or vapor disposed and contained within the reservoir 106 . in additional preferred embodiments , a color change is produced due to physical or chemical reaction of the volatile material with a component of the membrane or film 108 covering the reservoir 106 . in such embodiments , the membrane 108 turns from opaque when not in use to clear when in use , or from one color when in use to another color when not in use or when in an alternate mode of operation . it will be appreciated that , in distinction with the prior art , once the opaque membrane film of the present invention is activated , it becomes clear or transparent . thereafter , it will remain in this clear transparent state until the volatile material to be realeased is depleted . it will also be noted as a distinct and novel aspect of the present invention that while the container filled with the volatile material such as insecticide can be removed from the heater device , in which case the delivery of volatile material is terminated . however , as stated above , the film remains transparent clear until the reservoir is completely and totally depleted . the following is a description of exemplary tests conducted and data obtained therefrom . clarity or optical transmission measurement of the membrane or thin film of prior art and of the present invention were taken to determine the efficacy of the present invention . these tests were conducted under conditions specified by and similar to american standards and testing methods test method known as astm method d1003 . a slight difference in instrument geometry was made . haze ( percentage ) is calculated as ratio of y diffuse transmission and y total transmission . the following data in the table table 2 below was obtained using the methods and materials described herein : sample id haze polyethylene clear film with thickness of 1 mil 7 . 88 celgard polypropylene film before use - 1 mil thickness 86 . 90 celgard polyproylene film during use - 1 mil thickness 21 . 37 [ 0077 ] fig6 is a representative graph 500 of experimental data obtained during the investigation of a preferered embodiment of the apparatus and method the present invention . the graph 500 is a representation of the product end of life indication function of the present invention . expressed in terms of the percent haze on the x - axis and product use time in hours on the y - axis , the graph 500 shows the initial clearing of the opaque small - pore thin - film membrane from the point 510 at which it exists in the initial opaque state where it is inactivated and unloaded , until it reaches a point 520 of significant transparency . the film remains transparent through the greatest majority of the entire product use time , until a point 530 at which the volatile material in the reservoir is essentially exhausted . the opacity of the film membrane rises rapidly and the transparency is essentially gone at point 540 . during the comparatively short period of time between point 530 and point 540 , the reservoir is essentially already depleted or exhausted , and the only remaining diffusion is as a result of the transfer of individual molecules of volatile material formerly residing within pores in the membrane to a point outside of the membrane . it will be important to re - emphasize that one aspect of the present invention is the distinction between “ product use time ” and “ total time ”. therefore , while the graph 500 shown in fig5 is demonstrative of such system of the present invention which has a product use lifetime of about 300 hours , it will be understood that those 300 hours could be spread out over 25 continuous days of use or 300 days of use not more than about 1 hour per day to longer , depending upon total usage . for example , a system of the present invention rated to operate for 30 days consecutively for 10 hour intervals would be advantageous and effective for home use by all those in areas where mosquitoes or other insects , or unpleasant smells and aromas , etc ., are a nuisance . in comparison to the prior art , the present invention provides constant visualization throughout the useful lifetime of the system , i . e ., the period of time between points 520 and 530 , and the system can be used as little or as much as desired with essentially no increased hazing or diminution of clarity during that time period . thus , the visual indicator is a small - pore film which becomes opaque when there is essentially no effective remaining amount of volatile material in the system . furthermore , the present system is a non - contact film , it does not require contact with a liquid form of the volatile material . therefore , it can also be considered a form of clarifying membrane in the presence of any reserve or supply of volatile material . additionally , the optical properties of the film or membrane of the present invention operate within the visual range of the electromagnetic radiation spectrum of any of those having wavelengths between about 400 nannometers and about 700 nannometers . unless defined otherwise , all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs . although any methods and materials similar or equivalent to those described can be used in the practice or testing of the present invention , the preferred methods and materials are now described . all publications and patent documents referenced in this application are incorporated herein by reference . while the principles of the invention have been made clear in illustrative embodiments , there will be immediately obvious to those skilled in the art many modifications of structure , arrangement , proportions , the elements , materials , and components used in the practice of the invention , and otherwise , which are particularly adapted to specific environments and operative requirements without departing from those principles . the appended claims are intended to cover and embrace any and all such modifications , with the limits only of the true purview , spirit and scope of the invention .
a visual indicator microporous membrane that provides controlled - release of active ingredients , and prevents formulation leakage for use such as with an insecticidal or fragrance emanator device . during use , the semiporous membrane visually indicates transmission of active ingredient vapor to the consumer . these micropores that are normally opaque become saturated and turn from opaque to clear when in use , and when additional volatile material remains . upon depletion of the volatile material from the reservoir and subsequently from the membrane , the membrane turns opaque again . in a preferred embodiment , the container comprises a protective shield at least partially covering the porous membrane .