The four major types of agents are the tearing or lacrimating agent CN, the nauseating agent DM, the irritant agent CS, and the smoke producing agent HC. The 30 percent failure rate of chemical agents is due to improper delivery or application or unfavorable wind conditions. The equipment for outdoor scenarios has improved with the advent of foggers, however, the tactics used remain unchanged. Tactics for indoor scenarios have changed greatly as the major principle has become never to use burning or pyrotechnic grenades inside a dwelling; police officers are now obliged to use non-burning projectiles. Other advantages of the burst-on-impact projectiles used indoors are its accuracy, no throw back, and easy chemical decontamination. The Goliath and Ferret burst-on-impact projectiles are also barricade penetrators, capable of defeating hollow core and some solid core doors, garages, box springs, and some very light metal structures; they are most effective against glass. The drawbacks of this type of delivery system are that, sometimes, less liquid chemical agent is delivered than expected; angular impacts with glass or hollow core doors sprays some agent outside; curtains, ceilings, and carpets can absorb some of the agent; broken tail fins can cause unstable flight; and some projectiles fail to fragment or burst. Other chemical munitions available for indoor use are instantaneous discharge grenades, aerosol grenades, and muzzle-blast cartridges. Major chemical agent producers offer seminars and instructor-level courses in the use of all their munitions.