Clear particles so they wont randomly pop up in render


I’ve got this brutally annoying problem, I got some particles in my blender file that is flying around… like normal particles, however if I just start a video at a random frame then they will still be there, they got about 500 frames to die so they will last the whole video but when I press “Animation” to start making the video then after about 20 frames I start seeing particles that have yet not died from the last animation scene through the alt-a. So my question is, how do I solve this problem? Because particles spawning randomly on wrong places = wrong and ugly and makes me furious >_< aaaargh!!!