The original designs involved complex glass blowing, were difficult to clean and to reproduce accurately. The 20 l/min size is designed to produce particle fractions (> 10 µm, 10-4 µm, < 4 µm) that are closest to those likely to be agreed as international standards.

The Burkard version closely follows May's intermediate (20 l/min) size, accurately produced in anodised aluminium alloy (or stainless steel). Airtightness is ensured by vertical compression, releasing this allows the sampler to be dismantled for removal of the catch, and for cleaning. It can then be fitted and re-assembled before heat sterilisation and operation. The flow is controlled by a critical orifice built into the third stage. To ensure this accurate flow the vacuum pump must be capable of maintaining a pressure difference of at least 180 mm (7inches) of mercury. A 'stagnation-point shield' is provided to improve aspiration efficiency in moving air. To maintain the designed depth of collection fluid in the machined chambers it is recommended that 6 ml be added to each stage. (Not 4 ml as originally described).