is also monitored in many cases for securing health. There also is some monitoring of air pollution. In many cases, environmental standards such as via maximum pollution levels, regulation of chemicals, occupational hygiene requirements or consumer protection regulations establish some protection in combination with the monitoring. Preventative measures like vaccines and medical screenings are also important. Using PPE properly and getting the recommended vaccines and screenings can help decrease the spread of respiratory diseases, protecting the healthcare workers as well as their patients. Secondary prevention Secondary prevention deals with latent diseases and attempts to prevent an asymptomatic disease from progressing to symptomatic disease. Certain diseases can be classified as primary or secondary. This depends on definitions of what constitutes a disease, though, in general, primary prevention addresses the root cause of a disease or injury whereas secondary prevention aims to detect and treat a disease early on. Secondary prevention consists of "early diagnosis and prompt treatment" to contain the disease and prevent its spread to other individuals, and "disability limitation" to prevent potential future complications and disabilities from the disease. Early diagnosis and prompt treatment for a syphilis patient would include a course of antibiotics to destroy the pathogen and screening and treatment of any infants born to syphilitic mothers. Disability limitation for syphilitic patients includes continued check-ups on the heart, cerebrospinal fluid, and central nervous system of patients to curb any damaging effects such as blindness or paralysis. Tertiary prevention Finally, tertiary prevention attempts to reduce the damage caused by symptomatic disease by focusing on mental, physical, and social rehabilitation. Unlike secondary prevention, which aims to prevent disability, the objective of tertiary prevention is to maximize the remaining capabilities and functions of an already disabled patient. Goals of tertiary prevention include: preventing pain and damage, halting progression and complications from disease, and restoring the health and functions of the individuals affected by disease. For syphilitic patients, rehabilitation includes measures to prevent complete disability from the disease, such as implementing work-place adjustments for the blind and paralyzed or providing counseling to restore normal daily functions to the greatest extent possible. The general use of machinery that has adequate ventilation and airflow is suggested for these patients in order to halt progression and complications of disease. A study conducted in nursing homes to prevent diseases concluded that the use of evaporative humidifiers to maintain the indoor humidity within the range 40–60%