There are many reasons why companies invest in employee health services and in health screening for staff. Some requirements are driven by health and safety at work considerations and may be specific to the particular occupation (e.g. hearing tests within a factory environment). Some companies may put staff through pre-employment screening to assess their fitness for the job in question. Some may offer executive screening to senior staff hoping to prevent sudden illness and encourage a healthy lifestyle. Some may provide basic health assessments for all staff.