in describing preferred embodiments of the present invention illustrated in the figures , specific terminology is employed for the sake of clarity . the invention , however , is not intended to be limited to the specific terminology so selected , and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish a similar purpose . in that form of the preferred embodiment of the present invention chosen for purposes of illustration , fig1 shows personal defense spray gun 100 , preferably comprising a pistol shaped body 101 . preferably , body 101 comprises pistol grip portion 103 . the shape of pistol grip portion 103 is preferably selected such that personal defense spray gun 100 is easy to hold . pistol grip portion 103 preferably includes handgrips 103 a for providing a high - friction surface , or the like , such that pistol grip portion 103 may be securely grasped by a user . the shape of body 101 is further preferably selected such that body 101 mimics the shape of a firearm such that aiming personal defense spray gun 100 is aided by a user &# 39 ; s pervious experience with such firearms ( or toys , such as a water pistol that mimic the shape and aiming mechanics of such firearms ) and / or aided by the intuitive and ergonomic shape of body 101 . pistol grip portion 103 preferably further comprises an audible alarm generating means , such as speaker 121 , disposed therein . speaker 121 is preferably configured to provide an audible alarm signal , and , thus , it will be appreciated by one skilled in the art that the location or other specifics of the audible alarm generating means may be altered so long as an audible alarm signal is generated that is capable of attracting the attention of nearby persons and alerting them that assistance is needed , such as in an emergency situation , or that is capable of stunning or disorienting an attacker . pistol grip portion 103 preferably further comprises removable cap 123 for providing access to a power supply , such as one or more batteries 310 ( fig3 ). batteries 310 ( fig3 ) are preferably operably connected to speaker 121 to provide power thereto , and are preferably further operably connected to lighting means , such as led 125 to provide power thereto . led 125 may optionally be replaced with high - intensity led , laser , incandescent , fluorescent , neon , or other lighting means suitable for illuminating a target and / or stunning , disorienting , or visually impairing an attacker . body 101 preferably further comprises trigger 131 which is preferably operable by a user of personal defense spray gun 100 to discharge the personal defense spray as described in greater detail hereinbelow . safety switch 133 is preferably operably connected to trigger 131 and is preferably movable between at least first safe position 133 a and second fire position 133 b , wherein trigger 131 is inoperable , at least to discharge a spray , when safety switch 133 is in first safe position 133 a and is operable to discharge the personal defense spray when safety switch 133 is in second fire position 133 b . it will be understood by one skilled in the art that the personal defense spray may be a pepper spray , such as oleoresin capsicum or the like , or may be any other suitable non - lethal defense spray , including gel materials . likewise , other active sprays , such as animal repellants ( e . g . bear repellant , shark repellant , citronella , or mosquito repellant ), animal attractants ( e . g . deer scents , fishing scents or chum ), pest repellants , pest sprays , marking agents ( e . g . dyes or paints ), perfumes , deodorizers , fungicides , biocides , disinfectants , cleaning products , or other suitable liquid , gel , foam , or other agent or formula . as is also shown in fig1 , personal defense spray gun 100 preferably includes canister housing 141 for receiving a canister containing a personal defense spray , such as canister 600 ( fig2 ). body 101 preferably further includes biased ( e . g . spring - biased ) release button 143 operably connected to canister housing 141 for selectively retaining canister housing rear end 141 a disposed proximate body 101 , such that canister 600 is operably connected to trigger 131 . canister housing 141 is preferably hingedly attached to body 101 at canister housing front end 141 b by a hinge element , such as pin 145 . in operation , canister housing 141 is released from engagement with release button 143 by movement of release button 143 . upon such movement , canister housing rear end 141 a is free to swing away from body 101 by rotating about pin 145 . now referring to fig2 , canister housing 141 is shown in an open position , wherein canister housing rear end 141 a has been swung away from body 101 about pin 145 . canister housing 141 preferably includes latch 147 protruding from a lower surface thereof configured for releasable operable engagement with release button 143 such that engagement of latch 147 with release button 143 ensures that canister housing 141 remains in a closed position , with canister housing rear end 141 a disposed proximate body 101 and canister 600 operably connected to trigger 131 . when canister housing 141 is in the open position , canister 600 may preferably be removed from canister housing 141 and be replaced . for this purpose , slot 149 is preferably included in canister housing 141 to provide access to a portion of canister 600 , whereby a user can grip canister 600 and extract it from canister housing 141 . now referring to fig3 , personal defense spray gun 100 preferably includes a power supply , such as batteries 310 disposed in pistol grip portion 103 . according to a preferred embodiment , a plurality of batteries 310 are removably disposed in pistol grip portion 103 such that they are arranged in series connection and in electrical contact with leads of a circuit operably connected to speaker 121 and / or led 125 . batteries 310 are preferably retained in such electrical contact by cap 123 which preferably includes spring 127 for biasing batteries 310 within pistol grip portion 103 and in electrical contact with the leads and with each other . cap 123 is preferably threadably , or otherwise , connected to pistol grip portion 103 , and is preferably removable therefrom in order to provide access to batteries 310 for replacement of batteries 310 . as will be understood by one skilled in the art , alternative types of batteries and alternative arrangements are possible , and are within the scope of the invention . now referring to fig4 , canister housing 141 is preferably comprises rigid hollow tube 401 with integral front wall 403 and rear opening 405 , and is preferably configured in size and shape to receive and securely retain canister 600 therein . front wall 403 preferably includes opening 407 disposed centrally therethrough for allowing passage of a stream of spray , such as a personal defense spray , pepper spray , oleoresin capsicum spray , or other caustic or irritant fluid , from canister 600 to an environment outside canister housing 141 . front wall 403 further optionally includes nozzle - receiver 409 for receiving and securely retaining nozzle 605 therein . thus , when canister 600 is inserted into canister housing 141 , canister 600 is preferably securely retained centrally therein with nozzle 605 in secure engagement with nozzle - receiver 409 such that fluid passing through nozzle 605 preferably passes through opening 407 . ejector 411 is preferably mounted at a location of body 101 proximate canister housing front end 141 b and projects into canister housing 141 proximate front wall 403 . ejector 411 preferably comprises a substantially resilient member and remains substantially stationary as canister housing 141 rotates about pin 145 . thus , when canister housing is in the closed position , ejector 411 is disposed between front wall 403 and canister 600 and does not interfere with the engagement of nozzle 605 and nozzle - receiver 409 . as canister housing 141 is rotated about pin 145 to the open position , ejector 411 preferably engages canister 600 and preferably pushes canister 600 rearward through rear opening 405 . additionally , when a canister 600 is inserted in canister housing 141 in the open position , ejector 411 preferably prevents accidental actuation of nozzle 605 by being depressed upon contacting front wall 403 . finally , ejector 411 preferably biases canister 600 towards rear opening 405 such that when trigger 131 is not actuated , or when trigger 131 is released , nozzle 605 is not depressed and no spray leaves canister 600 . now referring again to fig2 , canister 600 preferably comprises a sealed rigid peripheral wall structure including bottom 601 , sidewall 602 , and top 603 defining interior space 600 a capable of containing fluid under pressure therein . top 603 preferably includes opening 604 and nozzle 605 disposed therein and in sealed engagement therewith . nozzle 605 is preferably selectively actuatable , by depressing nozzle 605 , to selectively release a fluid contained within canister 600 under pressure . canister 600 optionally includes flexible liner 610 disposed in interior space 600 a and in sealed engagement with nozzle 605 , such that a personal defense spray fluid may be hermetically contained within flexible liner 610 , isolated from bottom 601 , sidewall 602 , and top 603 , and isolated from a propellant fluid contained within interior space 600 a . use of flexible liner 610 allows for operation of personal defense spray gun 100 in any orientation because the propellant is separated from nozzle 605 by flexible liner 610 , thereby preventing the propellant from escaping canister 600 . since the propellant cannot escape canister 600 , personal defense spray fluid stored within flexible liner 610 will be forced out through nozzle 605 regardless of orientation . additionally , flexible liner 610 preferably prevents mixing of the propellant fluid and the personal defense spray fluid such that when personal defense spray fluid is released through nozzle 605 misting is avoided . preferably a liquid stream is propelled from canister 600 upon actuation of nozzle 605 . in operation , a user may preferably operate release button 143 thereby preferably disengaging canister housing 141 from body 101 at canister housing rear end 141 a . the user may then preferably rotate canister housing 141 about pin 145 such that an interior of canister housing 141 is accessible through rear opening 405 . the user may then preferably insert canister 600 into canister housing 141 with nozzle 605 disposed proximate opening 407 until top 603 engages ejector 411 . the user may then preferably rotate canister housing 141 about pin 145 until latch 147 engages and is retained by release button 143 . the user may then preferably move safety switch 133 from first safe position 133 a to second fire position 133 b and operate trigger 131 . operation of trigger 131 preferably pushes on bottom 601 , thereby preferably causing nozzle 605 to be depressed , and , thus , activated , preferably releasing personal defense spray though nozzle 605 under pressure . when trigger 131 is released , ejector 411 preferably biases canister 600 toward rear opening 405 thereby allowing nozzle 605 to return to an inactive position . operation of trigger 131 may optionally complete a circuit , thereby providing electrical power to speaker 121 and / or led 125 . alternatively , electrical power is supplied to speaker 121 and / or led 125 only when trigger 131 is operated with safety switch 133 in first safe position 133 a . when canister 600 is empty of personal defense spray fluid , or when canister 600 is empty of propellant , canister 600 must be replaced . in order to replace canister 600 , a user may preferably operate release button 143 thereby preferably disengaging canister housing 141 from body 101 at canister housing rear end 141 a . the user may then preferably rotate canister housing 141 about pin 145 such that ejector 411 preferably pushes canister 600 rearward through rear opening 405 . the user may then preferably remove canister 600 from canister housing 141 and insert a new canister 600 . once used , canister 600 may preferably be refilled with personal defense spray fluid , and reused . according to an alternative embodiment , a test canister , structurally similar to canister 600 , is provided . the test canister is preferably filled with water , optionally contained within a sealed liner similar to flexible liner 610 , and propellant fluid under pressure . the user may initially insert the test canister in canister housing 141 and operate all of the features of personal defense spray gun 100 in order to become familiar with the operation thereof without the risk of releasing any personal defense spray fluid , which may cause damage to nearby objects or harm to nearby individuals , including the user . when the user has completed a test of the features of personal defense spray gun 100 , the user may preferably then replace the test canister with canister 600 containing personal defense spray fluid . having , thus , described exemplary embodiments of the present invention , it should be noted by those skilled in the art that the within disclosures are exemplary only and that various other alternatives , adaptations , and modifications may be made within the scope and spirit of the present invention . accordingly , the present invention is not limited to the specific embodiments as illustrated herein , but is only limited by the following claims .