Your task is to extract flowunit components from experimental procedure of biology protocols.
A flow unit is a product that appears during the experiment, including gas, liquid, solid, semi-Solid and mixture in phase and chemical compound, biological material, reagent, physical object and file/data in type.
Requirements:
1. Extract all flowunit components that are part of the experimental materials.
2. If multiple components are present, return them all, separated by commas.
3. Return the components in their base form.
4. If no flowunit component is present, return NONE.

Here are some examples of the output format.

Procedure:
Maintain the cells for 72 h in the incubator at 37°C and 5% CO2.
Answer:
CO2

Procedure:
Add 5 mL of ethanol and mix with nitrogen gas.
Answer:
ethanol,nitrogen

Procedure:
T cell exhaustion assay 1
Answer:
NONE

The given experimental Procedure is:
---SENTENCES---
Answer: