It works at a very low concentration-10 parts per billion-so you can't smell the compound.
这种物质在极低浓度下(10ppb)就可以发挥作用，因此，你是闻不到这种物质的。
Wasps can smell chemicals in concentrations as tiny as a few parts per billion in the air.
黄蜂能够嗅出极小浓度的化学成份，哪怕它们在空气中的含量是十亿分之几个单位。
His proxies also argued that, as the current legal ozone limit-75 parts per billion-was up for review in 2013, it anyway made sense to delay reducing it.
他的代理人也指出，由于现在的法定臭氧限制是十亿分之七十五的浓度，已经足以应付2013年的审核，这无论如何都会帮助推迟臭氧量的减少。
To be sure, the concentrations of these pharmaceuticals are tiny, measured in quantities of parts per billion or trillion, far below the levels of a medical dose.
要肯定的是这些药物浓度极少，量是以每10亿或万亿为单位来计算。远远要低于医用水平。
The test method for determining residual vinyl chloride monomer content in parts per billion level in PVC resin by capillary column gas chromatography headspace technique is suggested.
提出用大口径毛细管顶空进样气相色谱法对聚氯乙烯树脂中十亿分之一级残留氯乙烯含量的测量方法。
The Breast Cancer Fund collected 2 samples of 6 different types of food marketed to children, and found levels of BPA ranging from 21 parts per billion (PPB) to 77.5 PPB, with an average of 49 PPB.
乳腺癌基金会选取了六种面向儿童市场的食物，并各抽取了两个样本进行研究。研究结果发现这些食物中双酚含量范围为十亿分之二十一到十亿分之七十七点五，平均含量为十亿分之四十九。
Researchers can still account for nearly every drop of water and watt of sunlight, track parts-per-billion flows of carbon and oxygen, and monitor every organism.
研究人员依然能够分析几乎每一滴水、每一瓦特阳光，能够追踪碳氧流量以及监测每一种生物体。
Atmospheric concentrations of carbon dioxide have reached 386 parts per million-and rising, because every year, human activity spews more than 30 billion metric tons of CO2.
目前大气中CO2(二氧化碳)的浓度已达百万分之386，而且还在上升。因为每年，人类活动要排放出300多亿吨CO2。
Atmospheric concentrations of carbon dioxide have reached 386 parts per million-and rising, because every year, human activity spews more than 30 billion metric tons of CO2.
目前大气中CO2(二氧化碳)的浓度已达百万分之386，而且还在上升。因为每年，人类活动要排放出300多亿吨CO2。
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