Since the shelf life is 2 years (agreed with UKAS) we make a new certified batch just before the expiration of the existing batch. The cost to certify is high so it is generally not viable to make batches more often; the point at which the cost spread across a batch becomes reasonable is around 150 units.
Please contact us to find out the current expiration dates of stock.
Body alcohol levels were originally measured from blood samples. When breath analysis began, it was necessary to find a relationship between blood and breath.
A retired former forensic scientist who had worked for the UK service told us of a survey carried out on a fairly large random sample of people, and the relationship
alcohol concentration in blood / alcohol concentration in breath
was found to vary between 1,600 and 2,900. Choosing a fixed point is therefore somewhat arbitrary, and the two ratios most used are around the median value, 2300/1 in the UK and 2100/1 in the USA.
It is important to realise that the breath values are absolute. In the UK the limit value is 35 micrograms of alcohol in 100 cm3 breath, which is 191.4 ppm ethanol, and this equates to 80mg/100 ml blood at 2300/1. In the US, an 80mg blood value is held to equate to 38 micrograms.
Some examples of national blood/breath standards:
- Australia 2300:1
- China 2200:1
- France 2000:1
- Germany 2100:1
- Italy 2100:1
- Poland 2100:1
- UK 2300:1
- USA 2100:1
Please consult with your country’s relevant regulatory body for the partition ratio used in your locality.
It depends on the level of accuracy you want. With a Guth type simulator with a 500ml bath, ten to twenty units might be the limit. If you use two simulators in tandem, then 50 to 100 is possible. Then discard the upstream contents, transfer the liquid from downstream to upstream, and finally replace the downstream standard.