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Shift work is an employment practice designed to make use of, or provide service across, all 24 hours of the clock each day of the week (abbreviated as 24/7). The practice typically sees the day divided into "shifts", set periods of time during which different groups of workers take up their posts. The term "shift work" includes both long-term night shifts and work schedules in which employees change or rotate shifts.
Shift work is considered a risk factor for many health problems. It has many negative cognitive effects (e.g., learning and memory deficits, loss of attention and vigilance). In addition, rotating night shift work disrupts our circadian clocks which is associated with a higher probability of developing obesity, diabetes and cardiovascular disease.
Shift work can also contribute to strain of marital, family, and personal relationships.
Health consequences 
Shift work increases the risk for the development of many disorders, including:
- Shift work sleep disorder (SWSD): Shift work sleep disorder is a circadian rhythm sleep disorder characterized by insomnia and excessive sleepiness. Shift work is considered sine qua non for the disorder.
- Breast cancer A 2005 review of earlier studies came to the result that women whose work involve night shifts have a 50% increased risk of developing breast cancer. This may be due to alterations in circadian rhythm: melatonin, a known tumor suppressant, is generally produced at night and late shifts may disrupt its production. The WHO's International Agency for Research on Cancer listed "shiftwork that involves circadian disruption" as a probable carcinogen in 2007 (IARC Press release No. 180).
- Possibly other types of cancer 
- Cluster headache
- Ischemic heart disease: Shift workers who had worked in that method for 15 years or more were three times more likely to develop ischemic heart disease.
- Poor sexual performance
- Appetite control: Shift work has been associated with a higher disposition for developing nutritional issues and obesity.
Shift work also can exacerbate symptoms and progression of chronic diseases, such as sleep disorders, digestive diseases, heart disease, hypertension, epilepsy, mental disorders, substance abuse, diabetes mellitus type 1, asthma, and health conditions that require medications with circadian changes in effectiveness.
UCSF neurologist Louis Ptacek, who studies circadian rhythms, genes and sleep behaviors, has been quoted: "It's not surprising, we have evolved on a planet that is rotating every 24 hours. Our internal clock is more than just when we sleep and wake. It's related to cell division and it regulates our immune systems. When we battle our internal clock, that has complications." Artificial lighting may additionally contribute to disturbed homeostasis.
Many shift workers use stimulants such as caffeine to stay awake at work and/or sleeping pills to aid with sleep during the day. However, both are addictive and should be used with care. There is currently no research on shiftworkers and long-term use of sleeping pills.
Mitigating the health consequences of shift work 
Though shift work itself remains necessary in many occupations, through various methods employers can alleviate some of the negative health consequences of shift work. The United States National Institute of Occupational Safety and Health recommends employers avoid quick shift changes, permanent night shifts, and several days of work offset by several days off. Employers should also attempt to minimize the number of consecutive night shifts, long work shifts and overtime work. Having a regular, predictable schedule can also diminish the negative health effects of shift work. A poor work environment can exacerbate the strain of shiftwork. Adequate lighting, clean air, proper heat and air conditioning, and reduced noise can all make shift work more bearable for workers. Also, appropriate sleep hygiene is recommended.
Employees can mitigate the effects of shift work by blocking out noise at home, maintaining a regular sleep routine, and avoiding heavy foods and alcohol before sleep. Exercise in the three hours before sleep can make it difficult to fall asleep, so workers might exercise before work instead.
Cognitive effects of shift work 
Compared with the day shift, incidents have been estimated to increase by 15% on evening shifts and 28% on night shifts.
One study suggests that, for those working a night shift (such as 23:00 to 07:00), it may be advantageous to sleep in the evening (14:00 to 22:00) rather than the morning (08:00 to 16:00). The study's evening sleep subjects had 37% fewer episodes of attentional impairment than the morning sleepers.
The circadian phase is relatively fixed in humans; attempting to shift it so that an individual is alert during the circadian bathyphase is difficult. Sleep during the day is shorter and less consolidated than night-time sleep.
The effects of sleep inertia wear off after 2–4 hours of wakefulness, such that most workers who wake up in the morning and go to work suffer some degree of sleep inertia at the beginning of their shift. The relative effects of sleep inertia vs. the other factors are hard to quantify; however, the benefits of napping appear to outweigh the cost associated with sleep inertia.
Cognitive effects of sleep deprivation 
Acute sleep deprivation occurs during long shifts with no breaks, as well as during night shifts when the worker sleeps in the morning and is awake during the afternoon, prior to the work shift. A night shift worker with poor daytime sleep may be awake for more than 18 hours by the end of his shift. The effects of acute sleep deprivation can be compared to impairment due to alcohol intoxication, with 19 hours of wakefulness corresponding to a BAC of 0.05%, and 24 hours of wakefulness corresponding to a BAC of 0.10%. Much of the effect of acute sleep deprivation can be countered by napping, with longer naps giving more benefit than shorter naps. Some industries, specifically the Fire Service, have traditionally allowed workers to sleep while on duty, between calls for service. In one study of EMS providers, 24 hour shifts were not associated with a higher frequency of negative safety outcomes when compared to shorter shifts.
Chronic sleep deficit occurs when a worker sleeps for fewer hours than is necessary over multiple days or weeks. The loss of two hours of nightly sleep for a week causes an impairment similar to those seen after 24 hours of wakefulness. After two weeks of such deficit, the lapses in performance are similar to those seen after 48 hours of continual wakefulness. The number of shifts worked in a month by EMS providers was positively correlated with the frequency of reported errors and adverse events. A study conducted by Defense Research & Development Canada found that "with respect to sustaining cognitive performance in the face of nocturnal alarms, clearly schedule 4 [24/72] is the best schedule and schedule 5 [another schedule with 24 hour shifts] is the second best." The study also compared three schedules with day and night shifts, and found the deleterious effects of multiple night shifts to be greater than those associated with long shifts.
Shift work management practices 
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The practices and policies put in place by managers of round-the-clock or 24/7 operations can significantly influence shift worker alertness (and hence safety) and performance.
Air traffic controllers typically work an 8-hour day, 5 days per week. Research has shown that when controllers remain "in position" for more than two hours, even at low traffic levels, performance can deteriorate rapidly, so they are typically placed "in position" for 30-minute intervals (with 30 minutes between intervals).
These practices and policies can be fairly obvious: selecting an appropriate shift schedule or rota and using an employee scheduling software to maintain it, setting the length of shifts, managing overtime, increasing lighting levels, or providing shift worker lifestyle training to help shift workers better handle issues such as understanding basic circadian physiology, sleep and napping, caffeine usage, social life issues, diet and nutrition, etc. They may also be more indirect: retirement compensation based on salary in the last few years of employment (which can encourage excessive overtime among older workers who may be less able to obtain adequate sleep), or screening and hiring of new shift workers that assesses adaptability to a shift work schedule.
A day may be divided into three shifts, each of 8 hours, and each employee works just one of those shifts; they might, for example, be midnight to 08:00, 08:00 to 16:00, 16:00 to midnight. Generally, "first shift" refers to the day shift, with "second shift" running from late afternoon to midnight or so, and "third shift" being the night shift. On occasion, more complex schedules are used, sometimes involving employees changing shifts, in order to operate during weekends as well, in which case there will be four or more sets of employees.
12-hour work shifts are also in use. In a modern steelworks, four sets of personnel are used, working consecutive days in one 12-hour shift (06:00 – 18:00 and vice-versa). Shift A will work days, and shift B nights, over a 48-hour period, before handing over to shifts C and D and taking 48 hours off. In the offshore petroleum industry, employees may work 14 consecutive days or nights, 06:00 – 18:00 or 18:00 – 06:00, followed by three or four weeks free. The svingskift (literally: "swing shift") in the offshore petroleum industry in Norway refers to a two-week tour during which employees work 12-hour days the first seven days and 12-hour nights the second (or vice versa).
Shift work was once characteristic primarily of the manufacturing industry, where it has a clear effect of increasing the use that can be made of capital equipment and allows for up to three times the production compared to just a day shift. It contrasts with the use of overtime to increase production at the margin. Both approaches incur higher wage costs. Although 2nd-shift worker efficiency levels are typically 3–5% below 1st shift, and 3rd shift 4–6% below 2nd shift, the productivity level, i.e. cost per employee, is often 25% to 40% lower on 2nd and 3rd shifts due to fixed costs which are "paid" by the first shift.
In general, requiring workers to live on a time-shifted schedule for extended periods is unpopular, and this typically must be paid for at a premium. It is common in heavy industry, particularly automobile and textile manufacturing and is becoming more common in locations where a shut-down of equipment would incur an extensive restart process. Food manufacturing plants, in particular, have extensive cleaning programs that are required before any restart. The use of shift work in manufacturing varies greatly from country to country. Shift work is common in the transportation sector as well. Some of the earliest instances appeared with the railroads, where freight trains have clear (i.e. passenger-free) tracks to run on at night. Shift work has been traditional in law enforcement and the armed forces: for example sailors must be available to handle a vessel around the clock, and a system of naval watches organized to ensure enough hands are on duty at any time. This is shift work by another name.
Service industries now increasingly operate on some shift system; for example a restaurant or convenience store will normally each day be open for much longer than a working day. Shift work is also the norm in governmental and private employment in fields related to public safety and healthcare, such as Emergency Medical Services, police, fire prevention, security and hospitals. Companies working in the field of meteorology, such as the National Weather Service and private forecasting companies, also utilize shift work, as constant monitoring of the weather is necessary.
3-day shift patterns 
The US Navy uses a three shift system that relies on an 18-hour day instead of a 24 hour day. The 24-hour period is broken up into 4 shifts. 00-06, 06-12, 12-18, and 18-00. A sailor will stand watch on his shift. During his offgoing shift he will have time to perform maintenance, work on qualifications and handle all his collateral duties. During the oncoming time the sailor has time to sleep, relax, and do whatever personal things he needs to do like laundry.
This does not apply to the attached air wing, which will work a 12 on, 12 off schedule 7 days a week.
|Pattern||Run 1||Run 2||Run 3|
Submarine sailors in the American Navy engage in a pattern known as sixes while underway. Instead of a 24-hour day, the ship operates on an 18-hour schedule. Any given individual is scheduled to stand watch for 6 hours, perform any other duties and engage in leisure time for 6 hours, then sleep for 6 hours. If enough personnel are available, a given watchstation may benefit from a fourth man referred to as the midnight cowboy. He will stand the same 6-hour watch in a given 24-hour period, usually from midnight to 06:00 (hence the midnight portion of the name, which is most often shortened to just cowboy) and the person who would normally stand that watch is free. This gives rise to a schedule of six on, twelve off, six on, thirty off, six on, twelve off.
4-day shift patterns 
In the 12/24/12/48 or 12/24 pattern, employees work in shifts of 12 hours; first a "daily shift" (e.g. 06:00 to 18:00), followed by 24 hours rest, then a "nightly shift" (18:00 to 06:00), finishing with 48 hours rest. This pattern needs four teams for full coverage, and makes an average 42-hour workweek. The pattern repeats in a 4-week cycle, i.e. over 28 days, and has 14 shifts per employee therein.
|Time||Week 1||Week 2||Week 3||Week 4|
|Pattern||Run 1||Run 2||Run 3||Run 4||Run 5||Run 6||Run 7|
5-day shift patterns 
In four on, one off the employee only gets one day off. There are 28 shifts per employee in a five-week cycle (i.e. 35 days), this adds up to an average of 48 hours worked per week with 8-hour shifts. This pattern is mainly adopted by industries in which companies prefers to work for all days of the week with four shifts and where laws do not let employees work for 12 hours a day for several days.
|Time||Week 1||Week 2||Week 3||Week 4||Week 5|
|Pattern||Run 1||Run 2||Run 3||Run 4||Run 5||Run 6||Run 7|
6-day shift patterns 
In four on, two off the employee only gets two days off. There are 28 shifts per employee in a six-week cycle (i.e. 42 days), this adds up to an average of 56 hours worked per week with 12-hour shifts, or 37 1⁄3 hours per week with 8-hour shifts. Three groups are needed for each time span, i.e. to cover the whole day and week a company needs 6 groups for 12-hour shifts or 9 groups for 8-hour shifts. This pattern is mainly adopted by industries in which employees do not engage in much physical activity.
|Shift||Week 1||Week 2||Week 3||Week 4||Week 5||Week 6|
|Pattern||Run 1||Run 2||Run 3||Run 4||Run 5||Run 6||Run 7|
Week shift patterns 
Three-shift system 
The three-shift system is the most common pattern for five 24-hour days per week. The "first shift" often runs from 06:00 to 14:00, "second shift" or "swing shift" from 14:00 to 22:00 and a "third shift" or "night shift" from 22:00 to 06:00. To provide coverage 24/7, employees have their days off ("weekends") on different days.
All of the shifts have desirable and less desirable qualities. First shift has very early starts, so time in the evening before is heavily cut short. The second shift occupies the times during which many people finish work and socialize. The third shift creates a situation in which the employee must sleep during the day.
Generally, employees stay with the same shift for a period of time, as opposed to cycling through them; this is seen as healthier.
To provide an overlap in shifts, some employers may require one of the shifts to work four 10 hour shifts per week (as opposed to five 8 hour shifts, both are 40 hours per week). In that scenario, the night shift might extend from 21:00 to 07:00, but the night-shift would have nearly four days off (86 hours) between work weeks. This change, along with first shift moving a half hour later, or second moving a half hour earlier, ensures at least a half hour overlap between shifts, which might be desirable if the business is open to the public to ensure that customers continue to be served during a shift change.
Some states, such as California, accommodate this arrangement by allowing the employee to be paid at their regular rate (as opposed to time-and-a-half, or an overtime rate, that would normally be required for any time past 8 hours) for the 10 hour shift, calling this an "alternative workweek".
Four on, three off 
In four on, three off, each employee works four days and gets a three-day weekend. For some types of manufacturing, this is a win-win arrangement. For example, a paint company had been making 3 batches of paint per day, Monday through Friday (3 × 5 = 15). They changed to making 4 batches of paint, Monday through Thursday (4 × 4 = 16). Total worker hours remained the same, but profits increased. In exchange for two additional hours of work per day, over 4 days, workers got an additional day off every week. See also the book, 4 Days, 40 Hours.
|4-day week||08:00–18:00||10 h||10 h||10 h||10 h||off||off||off|
|4½-day week||08:00–17:00||9 h||9 h||9 h||9 h||4 h||off||off|
|5-day week||09:00–17:00||8 h||8 h||8 h||8 h||8 h||off||off|
Continental shift 
Continental shift, adopted primarily in central Europe, is a rapidly changing three-shift system that is usually worked for seven days straight, after which employees are given time off, e.g. 3 mornings, 2 afternoons and then 2 nights.
24*7 shifts 
In the 24*7 pattern there are 24 consecutive shifts of 7 hours per week, hence covering 24/7. With 4 groups and 6 shifts per group, the work time is 42 hours per week. Several sub patterns are possible, but usually each group is responsible for one of four time slots per day. Each of these is 6 hours long and if a shift begins in their time slot, a group has to work it. This way there are 14, 21 or 42 hours of rest between shifts, every group gets one whole day off. Shifts can be swapped to make double-shifts and increase the minimum time of rest.
|Shift/Group||Work time window||Mon||Tue||Wed||Thu||Fri||Sat||Sun|
|Shift/Group||Work time window||Mon||Tue||Wed||Thu||Fri||Sat||Sun|
Split shift 
Split shift is used primarily in the catering, transport, hotel, and hospitality industry. Waiters and chefs work for four hours in the morning (to prepare and serve lunch), then four hours in the evening (for an evening meal). The average working day of a chef on split shifts could be 10:00 to 14:00 and then 17:00 to 21:00
Earlies and lates 
Earlies and lates is used primarily in industries such as customer service (help desk, phone-support), convenience stores, child care (day nurseries), and other businesses that require coverage greater than the average 09:00 to 17:00 working day in the UK. Employees work in two shifts that largely overlap, such as early shiftfrom 08:00 to 16:00 and late shift from 10:00 to 18:00
In businesses where two shifts are necessary to cover the day, earlies and lates may be combined with one double shift per week per worker. Six 7-hour shifts in five days and seven 6-hour shifts in six days both result in 42 hours per week.
8-day shift patterns 
Four on, four off is a shift pattern that is being heavily adopted in the United Kingdom and in some parts of the United States. An employee works for four days, usually in 12-hour shifts (7:00 to 7:00) then has four days off. While this creates a "48-hour week" (42-hour average over the year) with long shifts, it may be preferred because it shrinks the work week down to four days, and then gives the employee four days rest—double the time of a usual weekend. Due to the pattern, employees effectively work an eight-day week, and the days they work vary by "week". As with three-shift systems, most employees stay with the same shift rather than cycling through them.
|four on, four off||ten-fourteen||Week 1||Week 2|
Such shifts are popular within the Australian ambulance and fire sector, see 2-2-4. However it is often referred to as a ten-fourteen roster, as the day shift lasts for ten hours, with the night shift lasting fourteen. Extended night shifts such as these are often a double edged sword; on one hand crews on slower weeknight shifts, or those in areas of low demand will receive excellent levels of rest (when there are no calls for emergency services, crews are encouraged to rest if required). Conversely, those employed on high demand days such as weekend nights, or in particularly high demand areas, will often be required to be awake or working for their entire rostered shift. However due to the scheduled nature, most ambulance and fire employees can attempt to obtain sufficient rest before or after a particularly busy 14-hour night shift.
A variation of the four on, four off pattern is the two days, two nights, four off pattern of working. In this shift schedule, employees work 12-hour shifts from 06:00 to 18:00 on day shifts and from 18:00 to 06:00 on nights. This pattern is currently in use by HM Coastguard in the UK, and employs four separate teams to maintain 24/7 coverage.
|Time||Week 1||Week 2|
12-day shift patterns 
The 6 on, 6 off pattern consists of 3 days and 3 nights of work, then 6 days off. These will alternate between other crews, also known as teams, for a full 24/7 operation. The 12-day pattern repeats in a cycle of twelve weeks, i.e. 84 days.
|Shift||Week 1||Week 2|
|06:00 to 18:00||A||A||A||B||B||B||C||C||C||D||D||D||…|
|18:00 to 06:00||D||D||D||A||A||A||B||B||B||C||C||C||…|
Fortnight shift patterns 
Panama Schedule 
The Panama schedule follows a 2-2-3 pattern throughout a fortnight, in which shift workers generally are allowed every other Friday, Saturday, and Sunday off, with two additional days off during the week, although this may differ depending on organization and industry. The most common form utilizes four shifts, each working twelve hours, with two shifts generally paired together: A working days and B working nights while C and D are off, and vice versa. It is not uncommon for shifts to rotate between days and nights, most often with six months spent on nights and six on days. This shift is sometimes known as 2-2-3 or "two, two and three".
|Shift||Week 1||Week 2|
|06:00 to 18:00||A||A||C||C||A||A||A||C||C||A||A||C||C||C|
|18:00 to 06:00||B||B||D||D||B||B||B||D||D||B||B||D||D||D|
7-day fortnight shift 
In the 7-day fortnight shift or 2-3-2 pattern, employees work their allotted hours within 7 days rather than 10 in a fortnight, i.e. fourteen days and nights. Therefore, 41 hours per week equate to 82 hours per fortnight, which is worked in seven days, at 11–12 hours per shift. This shift structure is used in the broadcast television industry, as well as many law enforcement agencies, as well as health care fields such as nursing and clinical laboratories in the US.
|Shift||Week 1||Week 2|
One of the advantages of using this pattern is each shift pair, for example A and B, will get time off on weekends alternatively, because the schedule is fixed and does not drift.
Five and two 
The five and two or 3-2-2 pattern provides 24/7 coverage using 4 crews and 12-hour shifts over a fortnight. Average hours is 42 per week but contains a 60-hour week which can be challenging.
|Shift||Week 1||Week 2||Week 3||Week 4|
5/4/9s or Five/Four Nines is a mix of 5-day and 4-day work weeks. Employees work in two-week cycles. Week 1, the employee works 4 days of 9 hours followed by 1 day of 8 hours with 2 days off (i.e. 44 hours). Week 2, the employee works 4 days of 9 hours with 3 days off (i.e. 36 hours).
Like 8 hours a day for 5 days a week, this pattern works to 80-hours in a two-week pay-period. Since employees work on nine days per cycle, this pattern is also referred to as 9/80. The benefit to working an extra hour a day gives you a normal 2-day weekend followed by a long 3-day weekend the next. Typical working hours for this type of shift would be 06:00 to 15:30 (9 hours with 30 minutes lunch) and 06:00 to 14:30 (8 hours with 30 minutes lunch) on the 8-hour work day. Often the employer will alter the starting times (e.g., start at 07:00 or 08:00).
|Week 1||9 h||9 h||9 h||9 h||8 h||off||off|
|Week 2||9 h||9 h||9 h||9 h||off||off||off|
A variation, early weekend or 4½-day week, has the employees work every Friday, but only for 4 hours each. Their weekend thus starts with the Friday lunch break.
Long-term shift patterns 
DuPont 12-hour rotating shift 
The DuPont 12-hour rotating shift provides 24/7 coverage using 4 crews and 12-hour shifts while providing a week off. Average hours is 42 per week but contains a 72-hour week which can be challenging. It is used in several manufacturing industries in the US. Companies that have gone to this schedule have noticed a decrease in accidents plus more rest for employees, less call ins, and more coverage when crews are short handed. In all the schedule is designed to improve safety. A particular advantage of this pattern is that it can readily be slewed to fit business requirements. For example if less coverage is required on a Sunday, stand-alone shifts are avoided by scheduling the fourth night and first day of four on that day. This also has the additional benefit of the quick turnaround day between three shift days and nights also falling on a Sunday.
|Time||Week 1||Week 2||Week 3||Week 4|
Seven-day eight-hour rotating shift 
The seven-day eight-hour rotating shift provides 24/7 coverage using 8-hour shifts with 14 crews. It consists of a "morning shift" from 07:00 to 15:00, a "swing shift" from 15:00 to 22:30 and a "night shift" from 22:30 to 07:30. Each shift works for five days straight. The 8-hour shifts allow vacations and absences to be covered by splitting shifts or working double shifts. The run of day shifts is 56 hours, but the 8-hour shift provides time for some socializing after work.
This pattern was once common in the pulp and paper industry in the Western United States but has been largely replaced by a 8 days, 8 swing, 5 nights, 9 off, 8-hour rotation.
Graveyard shift 
Graveyard shift, night shift or third shift (3rd shift) means a shift of work running through the early hours of the morning, especially shifts from midnight until 08:00 or from 23:00 until 07:00. There is no certainty as to the origin of this phrase; according to Michael Quinion it is little more than "an evocative term for the night shift … when … your skin is clammy, there's sand behind your eyeballs, and the world is creepily silent, like the graveyard."
Employees who work on an on-call basis have no regular schedule. They agree as a condition of employment to report to work when they are called, 24 hours a day, 7 days a week. This is particularly common in American railroad employment, especially for train crews.
Firefighting schedules 
In many departments, firefighters work 24-hour shifts. They are authorized to sleep in the fire station at night but are still subject to calls for service the entire shift. Most departments split the 168 hour long week between 3 or 4 work groups (sometimes referred to as 'shifts' or 'platoon groups'), resulting in a 56 or 42 hour workweek, respectively. Some departments reduce the average workweek by scheduling an extra day off for each firefighter in the work group, frequently reducing a 56 hour workweek to a 48 hour workweek by scheduling a 24 hour "Kelly Day" every three weeks. Departments have many options for scheduling firefighters for coverage. One option is 24 on/48 off, where a firefighter will work 24 hours and have 48 hours off, regardless of the day of the week or the holidays. Often they will be scheduled in an A–B–C pattern. Thus, a firefighter will be assigned to A, B or C shift and work whenever that letter is on the calendar.
Most departments have found that a 24 hour work shift, with opportunistic sleeping between calls for service, is a valid means of avoiding some of the health and cognitive problems associated with shift work.
Three-platoon schedules 
The most basic three-platoon schedule is a straight rotation of 24-hour shifts among three platoon groups. This rota limits time off to 48 hours in a row, less than 66 hours off in a row most workers get each weekend. Workers on this schedule only get one short weekend off every three weeks, making it difficult to perform the social grooming required to build the support networks necessary to deal with the stressors associated with emergency response. Twenty-four hours off-duty is also the minimum required to completely recover from a period of acute sleep deficit.
Another option is known as a California roll, where some shifts will be close together but allow for several days off. This option gives a 96 hour break every 9th day, which is contiguous to the conventional weekend on two of nine weekends, with a third weekend providing a break that starts on Saturday morning. There is an opportunity to accumulate sleep debt over the three days of work, however this debt should be completely cleared over the four-day break. The nine-day rota that is repeated to fill the calendar.
A firefighter will work 24 hours on, 24 off, 24 on, 24 off, 24 on, 96 hours (4 days) off.
This rotation reduces the chronic sleep deficit accrued over the first two work days at the expense of a shorter long break. This schedule's long break coincides with a standard weekend exactly once every nine weeks. The four-day break could be retained by working a fourth day in the rotation - XOXOOXOXOOOO.
A firefighter will work one day, off one, work one, off two, work one, off four days.
A number of departments have investigated further work consolidation by allowing for a 48 hour work shift. Careful demand management would be required to avoid acute sleep deficit, however, firefighters should return to work fully recovered from the previous shift.
Kenneth B. Ellerbe chief of the District of Columbia Fire and Emergency Medical Services Department has proposed a schedule where firefighters work three-day shifts, followed by three night shifts, followed by three days off. It is likely that such a schedule would impact all four alertness factors associated with shift work, and result in a threat to public safety. It would result in exactly one break coinciding with the standard weekend every nine weeks. DDDNNNOOODDDNNNOOO
Four-platoon schedules 
The most basic four-platoon schedule is a straight rotation of 24-hour work shifts between four work work groups or platoons. This schedule works 48 hours per week for three weeks and 24 hours the fourth week, averaging 42 hours per week.
Another variation of the 24-hour shift schedule is a 4-platoon system, averaging 42 hours/week. Thus, the schedule is 24 on, 48 off, 24 on, 96 off, on a 4-day rotation.
Although the performance benefits of shorter shifts may not outweigh the performance costs of consecutive nights of work, some departments with four platoon groups work shorter shifts. Most such departments work a 10 hour day and a 14 hour night tour. This enables the firefighter to get relieved from work in the afternoon, commute home, spend time with family, and get a good night's sleep before returning to work in the morning. Schedules that only allow 12 hours, or less, between work shifts do not allow enough time to incorporate a healthy night of sleep, and therefore begin to accumulate sleep deficit even when the employee is working days.
On the 2-2-4 schedule, firefighters work two 10 hour days, two 14 hour nights, and then have four days off. In the Canadian Firefighter study, consecutive nights were shown to be more deleterious to performance than a single, long shift. After two consecutive nights, performance effectiveness was reduced to 75%, vs. 78% on a 24-hour shift. If the schedule induces sleep deficit during the day shift, this performance would be worse. This schedule's long break aligns with the conventional weekend for exactly two weeks out of eight.
The rota is: DDNNOOOO.
The 2-2-3 schedule is also known as the Panama Schedule, however, when firefighters work it, the shifts rotate from day to night between every break. Since the firefighters have a two-day break before any nights worked, they do not start the series of nights with an employment-related sleep deficit. They do work three nights in a row, which would result in chronic sleep deficit if alarms are received on each night, however, the third night is always a Sunday night, which is often less busy than other nights of the week. This schedule allows for a long break every other weekend.
The rota is DDOONNN OODDOOO NNOODDD OONNOOO
Industries requiring 24/7 cover are those that employ workers on a shift basis, for example:
- Customer service including call centers
- Death care (medical examiner or coroner)
- Emergency response systems
- Flight Test
- Health care
- Public utilities
See also 
- Circadian rhythm sleep disorders
- Eight-hour day
- Fatigue Avoidance Scheduling Tool
- Schedule (workplace)
- Shift work sleep disorder
- Split shift
- Timebar scheduling
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Further reading 
- Knutsson, A., Åkerstedt, T., Jonsson, B.G. & Orth-Gomer, K. (1986) 'Increased risk of ischaemic heart disease in shift workers'. Lancet, 2(8498), 89–92.
- Burr, Douglas Scott (2009) 'The Schedule Book', 'ISBN 978-1-4392-2674-2'.
- Miller, James C. (2006) 'Fundamentals of Shiftwork Scheduling', http://www.dtic.mil/docs/citations/ADA446688
- Scientific Symposium on the Health Effects of Shift Work, Toronto, 12 April 2010, hosted by the Occupational Cancer Research Centre and the Institute for Work & Health (IWH).
- CDC - Work Schedules: Shift Work and Long Work Hours - NIOSH Workplace Safety and Health Topic
- Three-hour night shift system, For a crew of three on a small boat at sea