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On the Ringelmann smoke chart, what approximate percentage blackness corresponds to “Chart No. 2”?

Difficulty: Easy

10 percent black
20 percent black
40 percent black
80 percent black
100 percent black

Correct Answer: 40 percent black

Explanation:

Introduction / Context:
The Ringelmann chart is a visual tool used to estimate smoke opacity from stacks by comparing plume darkness against standardized grayscale patterns. Each numbered chart level correlates with an approximate “percent black” or opacity.

Given Data / Assumptions:

We need the opacity that corresponds to Chart No. 2.
Standard mapping: 0 (0%), 1 (~20%), 2 (~40%), 3 (~60%), 4 (~80%), 5 (~100%).

Concept / Approach:
Memorize or reference the canonical mapping between Ringelmann numbers and percent blackness. Chart No. 2 is commonly taken as approximately 40 percent black/opacity.

Step-by-Step Solution:

1) Recall the sequence: 0, 20, 40, 60, 80, 100 percent for Ringelmann 0–5.2) Locate No. 2 → 40 percent.3) Choose the matching option.

Verification / Alternative check:
Environmental compliance guides and stack-observer manuals use this mapping for quick field estimates.

Why Other Options Are Wrong:

10%/20%: correspond to lighter plumes (No. 0–1).80%/100%: correspond to Ringelmann 4–5, much darker than No. 2.

Common Pitfalls:
Confusing percent blackness with percent light transmittance; environmental rules sometimes specify maximum Ringelmann numbers—knowing mappings avoids violations.

On the Ringelmann smoke chart, what approximate percentage blackness corresponds to “Chart No. 2”?

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