Neutral Density Filter Certification & Sales
NIST-Traceable Neutral Density Filter Certification
Environmental Monitor Service manufactures new neutral density filters and recertifies filters from EMS and other opacity-monitor manufacturers. Our certified filters are used for opacity monitor audits, calibration checks, preventive maintenance, and troubleshooting.
Every EMS filter is permanently identified with its optical density and corresponding opacity value. Certification documentation provides a dated, signed scan and traceability to National Institute of Standards and Technology (NIST) references.
Request neutral density filter pricing or call 800-864-2814 to discuss your audit-filter requirements.
What You Receive With Certification
- Verification of the filter’s optical density and corresponding opacity value
- A dated and signed certification record with a scanned trace
- Identification by a unique serial number
- Clear labeling of both optical density and percent opacity
- NIST-traceable certification documentation for your maintenance and audit records
Along with manufacturing our own neutral density filters, EMS offers industry-leading recertification of any competitor’s model.
Our filter certification service sets the industry standard for speed and cost. Contact us today for details.
Filters for EMS and Other Opacity Monitors
EMS can manufacture and certify new audit filters as well as recertify neutral density filters supplied with many other opacity-monitor systems. This gives facilities a single source for maintaining filter certification records across mixed equipment installations.
Filters are produced from precision optical substrate material and labeled with both optical density (O.D.) and percent opacity. If you are unsure which filter size or value fits your monitor, send us the manufacturer and model number and we will confirm compatibility.
Available Optical Density and Opacity Values
The table below lists our standard nominal optical-density values and their corresponding opacity percentages. Values of 1.00 O.D. and higher are available by special order.
| Nominal Density (O.D.) | % Opacity |
|---|---|
| 0.02 | 5.00 |
| 0.04 | 8.80 |
| 0.10 | 20.57 |
| 0.20 | 36.90 |
| 0.30 | 49.88 |
| 0.40 | 60.19 |
| 0.50 | 68.38 |
| 0.60 | 74.88 |
| 0.70 | 80.05 |
| 0.80 | 84.15 |
| 0.90 | 87.41 |
| 1.00 Up | 90.00 Up (Special Order) |
How to Send Filters for Recertification
- Contact EMS: Provide the monitor manufacturer, model, filter values, and quantity.
- Receive shipping instructions: We will confirm the service scope and where to send your filters.
- Certification: EMS verifies each filter and prepares the dated certification documentation.
- Return: Your filters and certification records are returned for use in your opacity-monitor audit program.
Request pricing, contact EMS, or call 800-864-2814. You can also review our complete opacity monitor service capabilities.
Neutral Density Filter Certification FAQs
Can EMS recertify filters from another manufacturer?
Yes. EMS recertifies neutral density filters supplied with EMS systems and filters from other opacity-monitor manufacturers.
Does EMS sell new neutral density filters?
Yes. EMS manufactures new precision neutral density filters in standard values, with higher values available by special order.
What information should I provide when requesting pricing?
Please provide the opacity-monitor manufacturer and model, the filter values or serial numbers, the number of filters, and whether you need new filters or recertification.
How often should neutral density filters be recertified?
Recertification frequency should follow your facility’s quality-assurance program and applicable regulatory or permit requirements. EMS can help you identify the appropriate service for your equipment and audit schedule.