3. Division of filtering self-rescuers for the population into large- and small-sized items

In gas-filtering engineering there is a practice of division of samples into products of large and small size. Such division is not simply formal. The establishment of type of the sample by dimensional characteristics at a planning stage and creating its sketch mostly defines projecting directions and approaches of design and development. For instance, such parameters, as charges volume, method of connecting absorbing system with the front part, design features of the front part, way of use in working and folded state, weight and volume of a product etc should be considered.

Besides, division by dimensional characteristics defines attempts of direct comparison of protective characteristics of the similar large- and small-sized products as senseless on default. Knowingly, that large gas-filtering canister can protect from higher concentrations than canister of the same model but of small size. These differences are initially considered at design stage according to various requirements to the products. Small dimension is an advantage but not considering protective properties.

Unfortunately there is division into products of small and large size for filtering self-rescuers. Standard ЕN 403/5/ says that self-rescuers are divided into two classes: S - for storage and M - for carrying. As a matter of fact it is the division by size and weight characteristics. But such division looks like lip service because there are no scopes for weight and volume of products of these classes and are established identical protective requirements for both classes. Such unity of requirements is senseless in division of self-rescuers into items suitable for everyday carrying and ready to use (small-sized) and the products intended for storage in people-crowded places (large-sized).

In our opinion, products weighing up to 0,20-0,25 kg and up to 0,5-0,6 dм3 of volume in folded state should be referred to self-rescuers of small size (the M-class by ЕN 403). With such characteristics product is considered as fit for carrying (just like folding umbrella) and, as a main point, within the limits of such weight and size there is a real opportunity to achieve minimal protective properties necessary to provide evacuation of people from dangerous zones in most of extreme situations. Situations with level of danger exceeding capabilities of small-sized products should be marked out in order to use means with higher protective characteristics (large size). The requirements to self-rescuers of a small and large size should be different respectively.