When you evaluate breathalyzers, the accuracy line in the spec sheet is usually the first number you compare. But that number only takes on a definite meaning together with the concentration at which it applies, the temperature of the test or guaranteed conditions, and the unit and test method. For a device that measures the alcohol concentration in breath, the same accuracy figure can lead to a different purchase decision depending on the concentration at which it was stated.
Conditions are especially easy to lose when you transfer quotes and product descriptions for several candidates into a single comparison table. If only the small number remains, values that actually came from different baselines start to look like a ranking. An accuracy spec becomes comparable information only when you read it as a bundle: not just "what it is," but "at what concentration and temperature, and stated in what way."
An accuracy figure starts from a reference concentration
Accuracy in a spec sheet is sometimes given as the error range at a specific concentration. If it is missing whether the value applies to a low or a higher concentration range, you cannot know the scope of the same number. You also need to distinguish whether only one reference point is given or whether different conditions are listed for several concentration ranges.
Look at the notation method as well. For example, stating error as a fixed value and stating it as a ratio of the reading produce numbers that look different. Rather than concluding from the numbers alone which method is better, it is safer to sort out, based on the original text, what each notation means across the concentration range you will actually use.
In your purchase comparison table, do not create a single accuracy column; give the reference concentration its own column. Even if you shorten the wording the supplier provided, it is important to carry it over so the concentration condition from the original material is not lost. If you leave figures without conditions as "unconfirmed," you reduce the chance of later finalizing a candidate on the number alone.
Temperature shows the environment the number applies to
Temperature is not extra information next to the accuracy figure; it is part of the conditions under which that value holds. If the spec sheet states a temperature, you cannot interpret the accuracy figure apart from that temperature condition. Conversely, if you cannot find a temperature condition, you should not make up an estimate of performance at the site temperature.
Testing before entry into a building and testing at an outdoor worksite affected by the seasons can involve different operating environments. Even so, you cannot conclude from the spec sheet alone that the device cannot be used outside a particular temperature range or how its accuracy changes there. What you need to do is put the expected place of use on site next to the conditions in the official materials and separate what matches from what needs further confirmation.
Temperature conditions also tie into the criteria for choosing an installation site. If you are planning a test area used by many people, you can consider including in the quote request not just whether there is room for the unit but how the space's temperature is controlled and how it will be used in each season. The supplier can then present the materials that fit those conditions of use.
Units and test methods must match before you compare
If the concentration units differ, you must not put the numbers side by side as they are. Check which unit the spec sheet, the screen display, and the quote each use, and where conversion is needed, keep the basis for the conversion together with the original value. Even with the same unit, if the test method or the applicable mode differs, it is hard to call it accuracy under the same conditions.
If you build your comparison table as below, you can avoid missing the conditions hidden behind the numbers. "Comparable" is not a verdict that one product is better; it is a column marking whether the figures can be reviewed on the same basis.
| Item to compare | What to transfer from the spec sheet | What to look at when judging |
|---|---|---|
| Accuracy notation | Error value and notation method | Whether it is a fixed value or a ratio, and whether the original wording is the same |
| Reference concentration | The concentration condition stated next to accuracy | Whether the candidates use the same concentration basis |
| Temperature conditions | The stated temperature or environmental conditions | Whether it can be compared with the actual installation and use location |
| Unit and test method | Concentration unit and the name of the mode | Whether you compared the same unit and the same method |
| Document applicability | Model name, document title, date checked | Whether it is material for the exact model under review |
How to organize a hypothetical comparison
Suppose a worksite is comparing two devices for pre-shift testing. Candidate A lists its accuracy figure together with the reference concentration, while candidate B shows only an accuracy figure in a quote summary table. In the observation step, rather than comparing the size of A's and B's numbers, first look for whether B's original spec sheet gives the concentration, temperature, unit, and test method.
In the interpretation step, classify the two numbers as not directly comparable because B's conditions have not been confirmed. A possible action is to ask, in the reply to the quote, for the official spec materials for the model under review and the conditions under which its accuracy applies, and to reorganize candidate A under the same items. The completion criterion is not picking the smaller number but reaching a state where, for both candidates, the model name, reference concentration, temperature, and unit or test method are confirmed, so you can judge whether the conditions are the same.
If you receive materials and one of them is a document for a different generation or a different model, do not use that document as evidence for that candidate. DATECH's official download page also has materials whose titles show the applicable model, such as "The New AF-50 / AF-50AD Korean manual." Compare document titles with model names like this so you do not apply materials for a product with a similar name directly to the current candidate.
How to record conditions in a request for quotation
When you request a quote, it is better to state the purpose of use and the conditions needed for comparison than to write only "a product with good accuracy." For example, specifying indoor or outdoor use, the expected installation location, the display unit you need, and the accuracy conditions you are comparing reduces the chance that the reply stays at abstract marketing language.
If a candidate is replaced or an option changes, do not keep building on the existing comparison table; match the model name and spec documents again. Seeing a value displayed on screen during a demo can help you check the operating flow, but that result alone does not verify all the concentration and temperature conditions in the spec sheet. In the comparison table, separating confirmed conditions, unconfirmed conditions, and items for which additional materials were requested is useful during purchase approval.
In the end, an accuracy spec sheet is not a document for ranking numbers but material for picking out candidates that fit your conditions of use. Compare figures only after you have confirmed that the concentration and temperature are on the same basis and have matched the unit, test method, and applicable model. Rather than forcing values with different conditions onto one line, separating them as not comparable helps prevent choosing a device that is under- or over-specified.
