The dead space of syringes differs between brands, and some do not meet the ISO standard. Needle dead space was 0.05 mL for 23 and 21 gauge, and 0.07 mL for 18 gauge, similar in order of magnitude to syringe dead space. For the 20, 30, 60 mL syringes the dead space was less than 0.2 mL.

For 5 mL syringes four of five brands, and for 10 mL syringes one of five brands failed to comply with the ISO the dead space was greater than 0.075 and 0.1 mL, respectively.

Syringe dead space for 1 and 2.5 mL was less than 0.07 mL.

Mean dead space was calculated for each syringe volume and needle gauge. A Mettler electronic balance was used for the measurements. The dead space of the needles was estimated using a similar technique: each needle was attached to a 1 mL syringe of known dead space. The difference in mass between the two measurements was calculated and converted to a volume based on the density of water. Syringe dead space was estimated by weighing each syringe, drawing up and expelling its rated volume of water for injection and re-weighing the syringe. Syringes of five brands and seven volumes: 1, 2.5, 5, 10, 20, 30, and 60 mL, 10 of each, 10 1 mL low dead space syringes and 10 23, 21 and 18 gauge needles were analysed. To measure the dead space of various syringe volumes and brands and a range of needles gauges commonly used in clinical practice, and to compare the results to the International Organization for Standardization (ISO) standard 7886-1:2018.

Dead space in 0.5 animal syringe