Plastic containers tend to avoid the leachables associated with glass, but have their own issues. Most plastics are innately permeable to atmospheric CO2. It is a slow diffution process that nevertheless does occur over time and can have a detectable impact on the conductivity of the samples, especially after significant precautions against CO2 intrusion are taken during sampling and testing of ultra-pure waters. However, in the absence of such precautions during sampling and testing, the atmospheric CO2 exposure during sampling alone will be the overwhelming influence on conductivity.