The apprenticeship will last between 18 and 24 months, where they will have to complete their Apprenticeship Log Book. The Log Book consists of 22 task areas with numerous sub tasks that must be completed before they achieve Performance of Maintenance (POM). Due to the inexperience of all new apprentices, ACS apprentices must be supervised by a qualified peer or supervisor while they are conducting aircraft maintenance repairs. Performance of Maintenance (POM) is the ability to be able to work by yourself and "sign" for your work, however, all POM work projects must be inspected and the paperwork can then be closed by the qualified technician. POM's are also the working force of the trade. After 4 years of working on aircraft, showing confidence, and the ability to perform aircraft maintenance properly, POM's can be recommended for Level "A" authorization. "A" Level is the authorization that allows a POM to sign for work and apprentices work. Level "A" Signatories typically tend to do more paperwork than hands on work as they are required to inspect all POM paperwork. The Level "A" signature certifies that the POM conducted a safe repair and that the associated paperwork is filled out completely and properly. As the Level "A" personnel are the only ones who can be granted the assessors authorization, they are also the teaching force for ACS Apprentices. Assessors are the only personnel who can sign off apprentice sub tasks as well as task areas, thus assessing their development as a technician. ACS techs typically work in shops and on hangar floors, but can also find themselves on ships, in the field, or on deployment to the Arctic or throughout the World. Repairs for some Aircraft Structures can be difficult to access, so aircraft stands, awkward positions, or confined space entry may be required. ACS techs are required to lift and move heavy stock, materials, parts and equipment, and are regularly required to work long hours in a standing position, sometimes wearing full chemical suits with boots, gloves, and respirator, inside a heated paint booth. ACS techs regularly come in contact with hazardous chemicals and materials, which include: Polyurethane paints, Methyl Ethyl Ketone (MEK), Zinc chromate paint primers, oils, jet fuel, paint strippers, and paint thinners. ACS techs are also exposed to noise, fumes, dust, odors, carcinogenic materials, and UV (welding) flashes. ACS techs use personal protective equipment (PPE) to reduce the risk of injury, but additional medical tests are used to monitor a technicians health above what is standard for most other Canadian Forces trades.