This is the 'aerosol type' I have. Can get refills (which I didn't know)
Walk Easy Personal Alarm
One press of the Walk Easy alarm blasts 138 decibels of ear piercing sound audible to up to ¼ of a mile away. Simply clip your Walk Easy onto your clothes or belt, while you jog, walk alone, use it to fire down the phone and stop nuisance calls, or keep it beside your bed for piece of mind at night. The Walk Easy personal alarm screeches for up to 6 minutes, works upside down, and will continue to work even if dropped on the ground.
* 138 decibel sound output
* Works even if used upside down
* More than six minutes continuous sound output or 300 intermittent blasts
* Attaches to a holster that clips on for practical, every day protection against attacks
* Provides personal protection for high school students, teenagers, security personnel, shop staff, elderly people and shift workers.
* When the cap is pushed down it will continue to work even if dropped to the ground
* Made in the United Kingdom
http://besafeinthecity.com/australi...t because I've always got my keys in my hand.