ANSI B11.19 Safety Distance Formula: How to Calculate Ds for Light Curtains in 2026

Frequently Asked Questions

What is the formula for light curtain safety distance?

The formula presented in the article is **Ds = K × (Ts + Tc + Tr + Tbm) + Dpf**. It combines approach speed, total stopping time, and depth penetration to determine the minimum safe distance.

Does OSHA require the ANSI B11.19 formula?

OSHA's general machine-guarding rule requires employees to be protected from machine hazards, but it does not give one universal light-curtain formula in that rule. Employers commonly use ANSI B11.19 to show the device was positioned and validated properly.

What time values should be included in the safety distance calculation?

The article includes machine stopping time, control-system stopping time, device response time, and any additional measured delay such as brake-monitoring time. Those values are added together before multiplying by the approach speed constant.

Do interlocks and two-hand controls use the same distance logic?

Yes. The article explains that the same principle applies: the hazard must reach a safe state before a person can access it, so total stopping time and real reach distance still matter.

When should a safety distance calculation be redone?

Recalculate when controls, tooling, speed, stopping performance, or access conditions change. The article also recommends rechecking after maintenance or other changes that could affect stopping time.