Turbidity standard. NTU value: 4000. Pack Size: 100ml. Highly accurate suspended polymer standards are approved by the EPA (Environment Protection Agency) and are suitable for use with most turbidity meters. All standards are Formazin free (non-carcinogenic) and non-toxic. Each standard is provided with a certificate of analysis. Please stipulate the turbidity value required (NTU) for standardisation. Turbidity standards for Ratio instruments. NTU value: 4000 Other NTU values are available. We can also supply these standards in 500ml packs. Please ask for details.