Effective November 10, 2010:
With three exceptions which are shown below, in South Dakota smoking is not allowed anywhere inside any business or inside any place of employment by anyone.  The ban applies to business owners and managers, employees, customers, and other people, and it applies anywhere on an employer's property that is enclosed.  The law does not prohibit smoking outdoors on business property.

More specifically:
South Dakota's smoking ban law says that no person may smoke tobacco or carry any lighted tobacco product in any public place or place of employment.

Under the law, a "public place" is defined as any enclosed area to which the public is invited or permitted. "Place of employment" is defined as an enclosed area under the control of a public or private employer. "Enclosed area" is defined as any space between a floor and a ceiling that is enclosed, exclusive of doorways, on all sides by permanent or temporary walls or windows.

Under the law, only the following businesses may allow smoking inside their establishments as of November 10, 2010:
1. sleeping rooms in lodging establishments. The rooms must be posted as a smoking room.
2. “cigar bars”: establishments with on-sale alcohol licenses; which generate 10% or more of their annual gross income from the sale of cigars; which have a humidor on the premises; which are enclosed by solid walls or windows, a ceiling and a solid door and are equipped with a ventilation system by which exhausted air is not recirculated to nonsmoking areas and smoke is not backstreamed into nonsmoking areas; which do not allow smoking of any tobacco products other than cigars and premium tobacco products purchased on the premises; and which were in compliance as of January 1, 2009.
3. retail tobacco stores which meet specific criteria: to be eligible for this exemption, the tobacco store must generate 65% or more of their annual gross income from the sale of tobacco, tobacco products and accessories for those products; must not allow alcohol consumption on the premises; and must be enclosed by solid walls or windows, a ceiling, and a solid door that provides egress to the outdoors.  Any retail tobacco store which meets those requirements must report annually to the Department of Revenue and Regulation the revenue generated from the sale of tobacco, tobacco products, and tobacco accessories as a percentage of annual gross income.

The law requires owners, managers, and operators of places where smoking is prohibited to inform violators of the smoking ban. The law doesn't specify the way in which the business must inform violators. The South Dakota Department of Health says on their website that window clings and signs are available as an option: https://apps.sd.gov/applications/PH18Publications/secure/Puborder.asp http://doh.sd.gov/catalog.aspx, or you can print a sign from their website at http://www.befreesd.com/SmokeFree_Signs_Generic300ppi.pdf