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| Device | Negative | Positive | Cost (U.S.$) | |
|---|---|---|---|---|
| Water Flow | ||||
| Bad | Emesis basin | Not accurate | Available | 2 |
| Better | Measuring cup | Not accurate | Available | 2 |
| Best | Graduated cylinder | Must order | Accurate | 12 |
| Air Flow | ||||
| Bad | Listen to flow | Not accurate | Available | Free |
| Better | Anemometer | Difficult to use | Small flow stream | 150 |
| Best | Air flow meter | Difficult to use | Accurate | 50 |
