MQ-2,MQ-6 MQ -135 should be used for industries or health?

I read that MQ-2,MQ-6 MQ -135 are not suitable/accurate enough for industrial or health applications.i want to know that if its true or not with reasons. can it be used in consumer electronics products?i have read the datasheet but it is difficult to get accurate readings as the air quality is already poor here.

They are cheap. They do not detect a single gas, but a number of gasses. The lifespan is not guaranteed. The heater requires more current than other sensors. The mechanical strength is poorly. And so on.

I think they are used in cheap consumer products. Those products are probably not safe and reliable. Try to find a test of breath analyzers for alcohol for consumers. They turn out to be very unreliable.