Adding a rotor blade (it had five on the main rotor and four on the tail) and using a modified exhaust system were among them.
增加一个桨叶(主桨有5个叶片，尾桨有4个)，并使用了改进的排气系统。
2
Conclusion The automobile exhaust was a main factor resulting in higher levels of saturation of carboxyhemoglobin in exposure group and had a certain impact on traffic policemen's health.
结论汽车废气是使外勤警碳氧血红蛋白饱和度增高的主要因素，已对交通警察产生一定的健康影响。
3
Engine exhaust noise is one of the main sources of automobile noise, and using of silencer is an important method controlling exhaust noise.