People often want a number. Change it every six months, or every twelve, or after so many hours. It is a completely reasonable thing to want, but a single figure can give false comfort, because filter life genuinely depends on how the cupboard is used. A better approach is to understand what shortens a filter's life and to plan around your own conditions.
What affects how long a filter lasts
A carbon filter has a finite capacity. Every molecule of vapour it captures uses up a little of that capacity, so the more it has to deal with, the sooner it is spent. The main factors are:
- How much you use, and how often. Heavy, daily use loads a filter far faster than occasional light work.
- What you are capturing. Some substances are held readily, others load the carbon quickly.
- Concentration and volume. Large quantities, or working close to the filter's limits, shorten life.
- Humidity and temperature. Conditions in the room affect how the carbon behaves.
Two identical cupboards in two different labs can have very different filter lifespans, purely because of how they are used. That is why copying someone else's schedule is not reliable.
Replace the filter before it stops protecting, not after. By the time a problem is obvious, the protection may already have lapsed.
Signs it is time, and their limits
There are some practical prompts to check a filter, but each comes with a caveat:
- An odour breaking through can be a sign, but many hazardous vapours have no smell, so a clean nose is not a clean bill of health.
- An airflow alarm is a prompt to investigate, though it tells you about airflow rather than filter saturation directly.
- A change in how the cupboard performs during testing is a strong signal.
Because none of these is a complete answer on its own, the safest approach combines them with a planned replacement schedule based on your usage.
A sensible approach to filter changes
- Log the date each filter is fitted, so you always know its age.
- Set a planned replacement interval based on your own usage, not a figure borrowed from elsewhere.
- Change prefilters regularly; they are inexpensive and they protect the main filter.
- Have filter condition considered as part of routine servicing and testing.
- If your work or volumes change, revisit the schedule.
Do not forget the prefilter
The prefilter is the unsung hero. It catches coarse dust and particulate before it reaches the main filter, which protects that more expensive filter and extends its life. Prefilters are cheap and easy to change, so changing them regularly is one of the simplest ways to get the most from the main filter behind them.
Getting the right replacement
When it is time, the replacement needs to be the right grade for your substances and the right size for your cabinet. Because we manufacture filters for our own and other manufacturers' cupboards, the simplest route is to tell us the cabinet and what you work with, and we will supply what fits.
Replacement filters, made to fit
Carbon, HEPA and custom-blended filters for our own and other makes of cabinet, matched to your work.