Inhibitory activity of pesticide-preventing active carbon fiber mask on the penetrations in pesticide spray and its inhibitory effect on acute inhalation toxicity in rats were s tudied. Pesticides were sprayed into box ($1.O{ imes}1.2{ mies}O.6;m$) at a dose of 20ml/min of diazinon ($Diatone^{TM}$) suspension (340ppm) and 5g/min of BPMC powder (2.0%) for 4 hours, and then captured the penetrated pesticides into water via mask in box under 8l/sec suction. The pesticides were analysed by A.O.A.C. method and GC/MS. Pesticide-preventing active carbon fiber mask significantly inhibited the penetration of diazinon by 93.4% as compared with control, and cotton mask and pesticide-preventing mask did it by 74.2% and 83.7%,respectively. This result shows that pesticide-preventing active carbon fiber mask has the most prominent inhibitory effect in preventing the penetration of diazinone. In the penetration of BPMC, all of three masks, such as active carbon fiber mask, cotton mask and pesticide-preventing mask, have a similar inhibitory effect, which were 99.3%, 98.6% and 97.0%, respectively. The penetrated pesticides via pesticide-preventmg active carbon fiber mask did not exert acute inhalation toxicity.