Defining a “non-toxic” gas by TLV range A gas is often termed practically non-toxic if its threshold limit value (TLV) is very high. Which TLV range (in ppm) best matches this description?

Introduction / Context:
Industrial hygienists classify gases by toxicity using threshold limit values (TLVs) or permissible exposure limits (PELs). A higher TLV means workers can be exposed to greater concentrations (time-weighted) with lower risk of adverse health effects. Recognising the order of magnitude helps in prioritising controls.

Given Data / Assumptions:

• TLV expressed in parts per million for gases/vapours.
• “Non-toxic” here is used in a comparative, practical sense, not implying no hazard at any concentration.
• Standard 8-hour workday exposure assumptions.

Concept / Approach:
Benign gases (e.g., nitrogen, oxygen within normal ranges, noble gases) are not assigned standard TLVs, but for many low-toxicity gases, occupational guidelines in the tens of thousands of ppm indicate relatively low intrinsic toxicity, with asphyxiation becoming the primary concern at very high concentrations due to oxygen displacement. Therefore, a TLV range of 10000–100000 ppm characterises practical non-toxicity compared with typical hazardous gases whose TLVs are far lower.

Step-by-Step Solution:

Verification / Alternative check:
Reference values for relatively low-toxicity species (e.g., some process inerts) are markedly higher than acutely toxic gases like H2S, NH3, or CO, which have TLVs in the single to triple digits.

Why Other Options Are Wrong:

Common Pitfalls:
Equating non-toxicity with safety; even “non-toxic” gases can displace oxygen and create deadly atmospheres in confined spaces.

Final Answer:
10000 to 100000