It is variable, but on the machine I am tested on acceptable levels of DLCO range from 31.7 - 48.1. There are a number of other factors you need to pay attention to besides just this value. Talk with your doctor about these.
The "acceptable noise level" will depend on your specific needs! What is "acceptable" in one situation, may be utterly unacceptable in another.
A decision based on what constitutes an acceptable level of risk
It depends to the acceptable risk level in your company. Usually AFR=10 is acceptable in most companies.
Couple percents.
AQL - acceptable quality level
It tries to attain an acceptable level of veracity.
40-45db
neither diffusion nnor perfusion limited
19.5
acceptable error level
one percent
The answer is a Threshold Value