Bacteria and mould contamination of working environment following a deep clean.

Following my previous assessment of bacteria and mould contamination in the workplace of this major manufacturer I have been asked to return to the factory and carry out a second evaluation following a major deep clean of the working areas. The employers has decided to clean the working areas despite the fact that the proviso assessment showed that the there is no bacteria and mould contamination at his workplace. The main reason for the clean was most likely to show employees that something is being done even though it was unnecessary.

During this second assessment I have concentrated only onto the areas described previously as problem. To establish the normal environment levels of bacterial and moulds in the air I Have collected air samples from outside the factory. These served as a baseline for my evaluation of the existing bacteria levels inside of the factory.


Microbiological samples for evaluation of airborne bacteria and moulds were collected in close proximity of the working machinery. The levels of airborne environmental bacterial were measured at 380 CFU/m3 and the levels of airborne environmental moulds were measured at 900 CFU/m3.


Following the collection of background samples further samples for both moulds and bacteria were collected from within the working environment. This time the levels of airborne moulds ranged between 600 CFU/m3 and 720 CFU/m3. The levels of airborne bacteria in the workplace ranged between 300 CFU/m3 and 420 CFU/m3.

Microbiological samples collected from the surfaces of the machines were collected from surfaces where aerosols are most likely to settle for air. The concentration of surface bacterial on various work surfaces ranged between 10 CFU/100cm2 and 66000 CFU/100cm2

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Based on the results of the assessment it can be concluded that the working atmosphere is not contaminated by excessive levels of airborne bacteria and fungi. The surface sample indicate that in some instance the level of surface bacteria have increased significantly in comparison to the samples collected from the same surfaces during the previous assessment. The levels of surface bacteria even at this level do not indicate a problem or abnormal situation. The bacterial levels can vary rapidly between days or after period of surfaces wetting. It is our opinion that unless the employees working in this area suffer from an identifiable bacterial infection the levels of surface bacteria recorded do not represent a risk to health.

By Tomas Gabor

Link through to Sysco - Nationwide specialists in hazard exposure monitoring
Hi, I have been working in my job as an Indoor Air Quality Investigator for a number of years and decided to share my experience with you. You can find lot of related information on my website toxic black mould
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  • Invekta

    Bacteria are all around us, even in the workplace that are less clean and disinfect That must take more care and more often implement measures cleansing and protection of workers.

    March 16, 2015, 10:40 am Link