Carbon Dioxide level in Walk-in cold boxes.

[phandai]

Good Morning kind folks,

I have a question and hope that this forum will be able to point me to the right direction. Basically, we have a couple of freezers and coldboxes (ave around 12000ft2 per box, 22ft height). We pick products from these boxes. Within the last year, with the people and working multiple shifts in the spaces, we measured CO2 level at or above OSHA limit. This create issues for the people and work continuity.

Does anyone here know of how make up air are done in freezers (-20C) and cooler (4C)? or any otherway to remediate for CO2 buildup in these enclosed space. We tried to keep the large sliding doors open, but this add heat to the space as well as moisture. The moister in freezer environment cause icing hazards on our floor.

I am hoping that someone who has already solved this issue in their facilities and can provide some guidance.

Regards,

Phandai.

[sedgy]

hi , what produce are you storing ? how many people at one time are working in the environment? and what kind of fresh air system have you? sedgy ,

[phandai]

Hi Thank you for your quick reply. We are storing liquid media (for cell growth). These are packed in liquid filled bottles and in boxes. The CO2 are generated by people working in the space due to 200% increase in shipment level. The walkin -20C boxes and the +4C boxes, none of these have make up air into the space. The make up air essential is through the large sliding doors and personnel doors when they are open. We tried to minimize the opening time due to temp requirements. We currently have 62 people per shift in these enviroment, picking orders.

I am trying to gage what is the industry practice for make up air in coldboxes such as these where people have to work in them continuously and if any economical solutions. Surely, I am thinking we are not doing anything out of the ordinary in our process, but I do not know of other industries.

Regards,


Phandai.

[sedgy]

hi phandai,
you have a problem = its eather , the workers pack the goods in an enjoining room , or you will have to have an air handling unit with fresh air intake, plus an extract fan ,
yes I can see you are trying to get fresh air in < through open doors < but who is to say there is any air draft through the cold room, but I can say definatly you will gain lots of heat , all the best for now , sedgy

[mad fridgie]

Your 4C room is not a problem, just install an air to air heat exchanger (forced flow and return) should be able to achieve around 75% efficiency, 10L/S/person.

The freezer room is a little more difficult, as the heat exchanger would freeze, so a defrost mechinism is required. Either a simple element within the heat exchanger chamber, or air defrosting using an arrary of dampers.

If in Both cases you do not want to go for the expense and/or not bothered about efficiency, then you force the fresh air into the room directly into the evaporator inlet air stream. This will stop any ice formation extrenal to the evap. Remember that you also require pressure relief in your rooms (heated in the case of the freezer)