The degree of laser power dangerous classifications are CI:<0.4mw, CII:0.4-1.0mW, CIIIA:1-5mW,  CIIIB:5-500mW, CIV:>500mW
    Manufacturer must put on warning labels on CII , CIIIA, CIIIB, CIV. 

1. CI:<0.4mW ( Not dangerous laser )

    This grade's laser has no any creature damage when being pointed , this level should be extreme safe for human because if point to skin , do not have any feeling , even use eye to see too . So it is absolutely safe . They might use on CD player or other small equipments .

2. CII:0.4-1.0mW ( Low power laser )

    This grade of laser won't injure skin , would not cause fire , and because of low power , when it point to human eyes ,  eye has enough time to blink , or turn head away to avoid these strong light . These are called "within reaction time " , the laser seems would not hurt people eyes too , but human eye can not see it for a long time , or it might cause hurt on Retina . 

3. CIIIA:1-5mW  ( Medium power laser )

     This grade laser still won't injure skin but in some situation , it might hurt eyes or even cause a blind . For example if laser beam pass lens , the laser beam might concentrate , then it become dangerous . This grade's laser should be signal light to show it is working or not . Better to have  a key switch too .

4. CIIIB:5-500mW  ( High power laser )

     This grade laser can hurt human eyes in whatever situation , as it is power higher enough , eyes has not enough time to blink , and people's skin can be injured , even it can cause a fire . Moreover , if point the laser to wall , the reflective light is still strong , it hurt eyes without sense . 

     This kind of laser should have Key switch , safety appliance , signal light , cut-off switch to stop laser at any time , warning label . It is better to wear laser protector for eyes before turn it on . 

5. More than 500mW ( Extreme Industry laser )

     This grade laser should mainly use on industry field or military field . For example laser cutting machine , imagine that the 1000mW CO2 laser can drill holes on steel plate ! Only typical man can touch the button switch . 

     However , according my practice :

     10-30MW has no feeling when use finger to touch laser beam , 30-50MW has little feeling of heat , 100-200MW feels quite hot , 200-600mW i dare not touch already , 1000mW i dare not go to see the beam . 

     Thanks your reading and sorry for my poor English .