parts per billion

Calibrations showed good linear relationship between photon counts of PMT and concentration of ozone generated by standard ozone calibrator, up to 50 ppb ( parts per billion by volume).

采用标准臭氧发生器标定的结果显示，在0￣50×10-9（体积比）的浓度范围内，化学发光的光子计数值与臭氧浓度之间的线性关系很好。

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。

His proxies also argued that, as the current legal ozone limit 75 parts per billion was up for review in2013, 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。

One thing worthy of note is that the detection limit of BRB is at the parts per billion level, which can satisfy the requirement of Environmental Protection Agency ( EPA).

值得一提的是，BRB检测极限甚至可达ppb级，达到了环境保护局（EPA）对汞离子的检测要求。

Theories and Technique Studies on Ultra-Violet Fluorescence Detection of Sulfur Dioxide in Air at the Parts Per Billion Level

Ppb级大气二氧化硫紫外荧光检测理论与实现技术研究

It's called ( E, E)-2,4-Undecadienal. It works at a very low concentration-10 parts per billion-so you can't smell the compound.

这种物质的化学名字叫E，E-2,4-十一烷二烯醛。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。