1 For best results from your flask, before use, pre-fill for about 3 minutes, using either hot water for hot drinks or cold water for chilled drinks. 2  Never use a microwave or conventional oven to pre-heat your flask.  If your flask has not been used for some time, rinse with warm water to remove any residual odours.
2. : the degree to which something is prevalent; especially: the percentage of a population that is affected with a particular disease at a given time.
In epidemiology, point prevalence is a measure of the proportion of people in a population who have a disease or condition at a particular time, such as a particular date. It is like a snap shot of the disease in time.It can be used for statistics on the occurrence of chronic diseases.ifetime prevalence (LTP) is the proportion of a population that at some point in their life (up to the time of assessment) have experienced the condition. Prevalence estimates are used by epidemiologists, health care providers, government agencies, and insurers.