[More than 30 grams (approximately 1 ounce) of sample less than 420µm required; more than 300 grams (approximately 0.67 pounds) of sample less than 420 µm required if testing metal dusts.] ...

For purposes of testing, approval, and area classification, the Code groups various air mixtures and presents them in Sec. 500.6 of the 2011 NEC. As noted in 500.6(B)(1), Group E is defined as ...

China plans to collect new samples of com-bustible ice — a kind of natural gas hydrate — from the northern part of the South China Sea next year, a senior official said.

[More than 30 grams (approximately 1 ounce) of sample less than 420µm required; more than 300 grams (approximately 0.67 pounds) of sample less than 420 µm required if testing metal dusts.] ...

Combustible Dust Basics: How to Collect a Sample and What Does a Go/No-Go Test Mean? Any activity that creates dust should be investigated to see whether there is a risk of that dust being combustible ...