After the ground fresh air enters the mine, it is polluted by the dust generated by rock drilling, blasting, loading, transportation, etc., as well as the harmful gases generated by the decay of the pit wood and the oxidation of the ore, thus becoming dirty air in the underground. Its composition is quite different from the fresh air on the ground, mainly due to increased dust, increased harmful gas content, and reduced oxygen content in the air.
In order to reduce the dust content and harmful gas concentration in the downhole air and increase the oxygen content to meet the national sanitary standards, mine ventilation must be carried out, that is, the ground fresh air is continuously sent to the well, and the dirty air from the well is discharged to the surface. Downhole temperature and humidity create comfortable working conditions to ensure the health and safety of underground workers.high quality Tennis Ball- Felt Pressurized Tennis Balls
Training tennis balls represent the standard by which all other tennis balls are measured with consistent feel and playability every time you step onto the court. Also can be Pet Tennis Balls for Dogs
Made of Durable Materials
Tennis Paddle Ball feature a controlled fiber release for consistent nap, natural rubber for consistent feel and reduced shock, and interlocked wool fiber for longer wear.
Official Ball of USTA Leagues
the Official Ball of USTA Leagues. They are USTA and ITF approved (USTA National Campus, 2019) and is available in extra-duty felt, regular duty felt, or extra-duty high altitude felt.
Training Tennis Balls, Tennis Paddle Ball, Pet Tennis Balls for Dogs, professional tennis ball, practice training ball, tennis ball ractets
Huizhou City Melors Plastic Products Co., Limited , https://www.evadecking.com