LAF & RLAF - difference & principles

Why we use RLAF for sampling / dispensing of R.M. ? What happens if we use LAF instead of RLAF ?

Reverse Laminar Air Flow is a purifying apparatus fitted with a high-efficiency HEPA filter to ensure maximum protection from airborne contaminants produced at the time of powder handling operations such as charging, sampling, and dispensing. It operates on a re-circulatory airflow principle which ensures to draw powder aerosols away from the operator and the operating environment thereby protecting products and providing safe working conditions for personnel. The reverse flow-scavenging pre-filter at the bottom at the bottom level / table level ensures that aerosolized particles are picked up at the source without being allowed to disperse into the area.